Coreless roll of absorbent sheet and method for manufacturing the same

ABSTRACT

A coreless roll of an absorbent sheet product, such as napkins, toilet paper, towels, etc., is provided made of a spirally wound continuous web of absorbent material having a first end and a second end, wherein a coating composition comprising a specific polymer is coated onto the continuous web. The coreless roll has excellent resistance to collapsing, as well as excellent flexibility, elasticity and resiliency. Moreover, the coreless roll has excellent disintegrability in water and can be used up over its whole length. A process for the manufacture of the coreless roll is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a national stage entry under 35 U.S.C. § 371 of, and claims priority to, International Application No. PCT/IB2017/001403, filed Sep. 29, 2017, the disclosure of which is hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a coreless roll of an absorbent sheet product such as napkins, toilet paper, towels, etc. In an aspect of the present invention, the coreless roll is provided in a compressed form. The present invention also pertains to a process for the manufacture of the coreless roll.

BACKGROUND OF THE INVENTION

Absorbent sheet products in rolled form find extensive use in modern society. Rolls of toilet paper, towels such as household (kitchen) towels or hand towels, etc., are staple items of commerce.

Rolls of absorbent sheet product for home use (e.g., toilet paper) typically consist of a continuous web of absorbent sheet material that is spirally wound around a prefabricated core made of a stiff material such as cardboard or glued paper. The core defines an axial hollow passageway, which is centrally positioned relative to the roll and extends from one edge of the roll to the other edge. The axial hollow passageway enables the consumer to easily mount the roll on the spindle of a roll holder. However, the core is expensive, requires storage space and additional manual handling. Furthermore, the core remains after use of the absorbent sheet product, thus increasing the risk of clogging sewage systems.

To address these concerns, “coreless” rolls and rolls with water-soluble cores have been developed. Among the most important properties of these products are their resistance to collapsing and their flexibility/elasticity.

“Collapsing”, as used herein, refers to the phenomenon occurring when the absorbent sheet product constituting the first inner turns of the roll (i.e., the turns forming the axial hollow passageway at winding start) cannot be stably maintained such that an axial hollow passageway is clearly defined. Coreless rolls are generally associated with an increased risk of “collapsing”. Collapsing typically occurs in the manufacture process of coreless rolls when the temporary core is extracted after completing the winding, or during storage and transport of the finished product. As a consequence of collapsing, it can become difficult to mount the roll on the spindle of a roll holder. Moreover, collapsing generally creates the perception of decreased quality among consumers.

A “flexible” roll offers the benefit that it can be provided in a compressed form, which requires less space during storage and transport. As a result, storage and transport costs can be significantly reduced. The roll can be compressed by applying and maintaining pressure in a direction perpendicular to the axial hollow passage so as to produce a roll having an oval cross section. The roll can be maintained in the compressed form during storage and transport by, e.g., tightly wrapping a packaging material around the roll(s).

The roll must also exhibit a certain level of “elasticity” such that it can substantially return by itself from the compressed (oval) form to the uncompressed (cylindrical) form (e.g., when the package is opened) while reopening the axial hollow passageway in a clearly defined manner. That is, the axial hollow passageway must open by itself and be clearly defined when the roll returns to the cylindrical form. This requires the first inner turns to newly and stably maintain the axial hollow passageway. As a result, there should be no substantially visible difference in appearance between a roll returning from the compressed form to the uncompressed form and a roll that has not been subjected to compression.

Furthermore, the roll can be subjected to deformation forces during storage and transport, e.g., radial forces exerted in the rewinding and/or cutting unit, axial forces occurring during packaging and/or when packaged roll products are stacked on pallets for storage/shipment, etc. As a consequence of deformation forces, the continuous web of absorbent material can be irreversibly deformed and the roll can lose its cylindrical shape, thus causing a feeling of decreased quality among consumers. Hence, the roll must combine a certain level of axial and radial stiffness (sometimes also referred to as “rigidity”) with excellent resiliency, meaning that the roll can recover its original size and shape when deformation forces are no longer applied. This requires the continuous web of absorbent material constituting the roll to exhibit suitable internal resistance to deformation. Hence, the roll should maintain its size and shape irrespective of whether it has been subjected to external deformation forces and/or to compression.

The prior art describes processes for achieving rolls of absorbent sheet product which are said to be flexible and can be provided in the compressed form.

WO 2009/027874 A1 discloses a roll including a nonwoven tissue web that is spirally wound around a flexible core. The flexible core includes a polymeric sheet of synthetic polymers, which is attached to the inner layer of the nonwoven tissue web by means of an attachment mechanism such as an adhesive, heat bonding, etc. The flexible core is characterized by a higher tensile strength in the machine direction than that of the nonwoven tissue web. As a result, the roll exhibits flexibility for packaging and storage purposes.

However, the polymer sheet of synthetic polymers is prepared beforehand, stored, and manually handled. Furthermore, in the frame of industrial manufacturing, the continuous web of absorbent material is run at a speed of around 10 m/s. This renders the incorporation and attachment of the polymer sheet to the inner layer of the nonwoven tissue web technically complex and difficult to implement at the running speed required for industrial manufacturing.

Moreover, the nonwoven tissue web forming the roll lacks elasticity. As a consequence, when the roll returns from the compressed form to the uncompressed form and/or is subjected to external mechanical constraints, the nonwoven tissue web that is spirally wound about the flexible core does not recover its original position and the roll retains an oval shape, i.e., it exhibits low resiliency. This contributes to a feeling of decreased quality among consumers.

WO 95/13183 A1 discloses a roll of elongated material having a core at the center of the roll. The core essentially includes a number of turns of the elongated material, which are fixed together by means of a binder such as polyvinyl acetate, polyacrylate, latex, starch, polyvinyl alcohol, etc. WO 95/13183 A1 also discloses a process for producing such roll in the compressed form. More specifically, WO 95/13183 A1 indicates that a binder solution is sprayed or coated on the first turns of a conventional winding. After complete winding and removal from the winding shaft, the roll is immediately compressed to an elliptical or oval section form. The document teaches that the roll can be opened from the compressed form by applying pressure on the “shorter” sides of the ellipse.

However, the binder as described in WO 95/13183 A1 (e.g., latex, starch, polyvinyl alcohol, etc.) produces a stiff core which includes a number of turns of glued elongated material. Hence, the resulting core lacks flexibility and shows low elasticity. As a result, after the roll has been compressed, it is difficult to reopen the axial hollow passageway in a manner leading to a well-defined axial hollow passageway. Furthermore, the first inner turns of elongated material (i.e., the turns of elongated material forming the core) are cohesively maintained together by the binder. The delamination force needed for separating the first inner turns is generally greater than the tear strength of the elongated absorbent material. It is hence difficult to separate the first inner turns without tearing apart the elongated material on which the binder is applied. As a result, it is not possible to use the elongated absorbent material on its whole length, i.e., up to the last sheet.

Moreover, the elongated material lacks sufficient elasticity. As a consequence, when the roll returns from the compressed form to the uncompressed form and/or is subject to external mechanical constraints, the elongated material forming the roll does not substantially recover its original position and the spirally wound elongated material does not substantially recover its original position and the roll retains an oval shape, i.e., it exhibits low resiliency. This contributes to a perception of decreased quality among consumers.

It is hence desired to provide a coreless roll of an absorbent sheet product which combines superior resiliency (and thus also appropriate flexibility and elasticity), good stiffness and good resistance to collapsing with a suitable delamination force.

It is also desired to provide a roll of an absorbent sheet product which can be used over essentially its whole length (i.e., essentially up to the last sheet) and prevents sewage systems from clogging up (disintegration time).

It is also desired to provide a coreless roll of an absorbent sheet product that can be provided in the compressed form wherein, after the roll has been compressed, it can substantially recover its original shape and size and the axial hollow passageway can be substantially reopened in a manner leading to a well-defined axial hollow passageway.

It is also desired to provide a process for manufacturing such coreless roll of an absorbent sheet product.

SUMMARY OF THE INVENTION

The present invention relates (according to “item 1”) to a coreless roll of an absorbent sheet product such as napkins, toilet paper, towels, etc., made of a continuous web of absorbent material having a first end and a second end, the continuous web of absorbent material being spirally wound such as to define an axial hollow passageway centrally positioned relative to the coreless roll and extending from one edge to another edge of the coreless roll and such that the first end is located on the outer side of the roll and the second end is located at the axial hollow passageway.

The spirally wound continuous web of absorbent material has a density of from 50 to 140 mg/cm³, preferably of 60 to 130 mg/cm³, more preferably of 70 to 120 mg/cm³.

At least the last turn located at the second end of the continuous web of absorbent material comprises a coating composition comprising a (preferably nonionic) polymer including oxygen and/or nitrogen atoms, a turn being one circumvolution of the spirally wound continuous web about the axial hollow passageway.

At least 20%, preferably at least 25%, more preferably at least 30%, more preferably at least 35%, more preferably at least 40%, more preferably at least 50%, more preferably at least 70% of the entire length of the continuous web of absorbent material in the machine direction comprises a coating composition comprising a nonionic polymer including oxygen and/or nitrogen atoms.

The present invention also relates to such coreless roll which is provided in the compressed form.

In one aspect of the present invention, the coating composition applied to the second end is the same as that applied over the entire length of the continuous web of absorbent material.

In one further aspect of the present invention, the coating composition is applied to the continuous web of absorbent material such that the maximum intersheet adhesion between the coated portions of the continuous web and the portions of the continuous web being in contact therewith is of from 0.3 to 1.7N.

In one further aspect of the present invention, the nonionic polymer is a nonionic cellulose ether such as an alkyl cellulose ether, a hydroxyalkyl cellulose ether or combinations thereof, or a polyether polyol such as a polyethylene glycol, a polypropylene glycol or combinations thereof.

The present invention includes the following embodiments (“Items”):

1. A coreless roll of an absorbent sheet product made of a spirally wound continuous web of absorbent material having a first end and a second end, the web of absorbent material being wound such as to define an axial hollow passageway centrally positioned relative to the coreless roll and extending from one edge to another edge of the coreless roll and such that the first end is located on the outer side of the roll and the second end is located at the axial hollow passageway; wherein the spirally wound continuous web of absorbent material has a density of from 50 to 140 mg/cm³, preferably of 60 to 130 mg/cm³, more preferably of 70 to 120 mg/cm³;

wherein at least a last turn located at the second end of the continuous web of absorbent material comprises a coating composition comprising a polymer including oxygen and/or nitrogen atoms, a turn being one circumvolution of the spirally wound continuous web about the axial hollow passageway; and

wherein at least 20%, preferably at least 25%, more preferably at least 30%, more preferably at least 35%, more preferably at least 40%, more preferably at least 50%, more preferably at least 70% of the entire length of the continuous web of absorbent material in the machine direction comprises a coating composition comprising a nonionic polymer including oxygen and/or nitrogen atoms.

2. The coreless roll of item 1, wherein the coating composition is applied to only one side of the continuous web of absorbent material, preferably the side oriented towards the axial hollow passageway. 3. The coreless roll of item 1 or 2, wherein the polymer including oxygen and/or nitrogen atoms comprised in the coating composition applied to the last turn(s) located at the second end is a nonionic polymer, and preferably said coating composition is the same as that applied over at least 20% of the entire length of the continuous web of absorbent material. 4. The coreless roll of any of item 1 to 3, wherein the maximum intersheet adhesion between the coated portions of the continuous web of absorbent material and the portions of the continuous web being in contact therewith is of from 0.3 to 1.7N. 5. The coreless roll of any of items 1 to 4, wherein the coating composition that is applied to the continuous web of absorbent material has an ionic demand of −1000 to +100 μeq/g, preferably of −500 to +50 μeq/g, more preferably of −50 to 0 μeq/g. 6. The coreless roll of any of items 1 to 5, wherein the nonionic polymer comprises at least one repeating unit comprising one or more oxygen and/or one or more nitrogen atoms. 7. The coreless roll of item 6, wherein the nonionic polymer comprises at least one repeating unit comprising one or more ether oxygen atoms and/or one or more hydroxyl groups. 8. The coreless roll of item 6 or 7, wherein on average at least 50%, preferably at least 80%, of all repeating units constituting the nonionic polymer comprise one or more oxygen and/or one or more nitrogen atoms, preferably one or more ether oxygen atoms and/or one or more hydroxyl groups. 9. The coreless roll of any of items 1 to 8, wherein the nonionic polymer is a nonionic cellulose ether. 10. The coreless roll of item 9, wherein the nonionic cellulose ether has a number-average molecular weight of 1,000 to 1,000,000, preferably of 2,000 to 500,000, more preferably of 3,000 to 200,000, more preferably 5,000 to 100,000. 11. The coreless roll of item 9 or 10, wherein the nonionic cellulose ether is an alkyl cellulose ether such as methylcellulose or ethylcellulose, a hydroxyalkyl cellulose ether such as hydroxyethyl cellulose or hydroxypropyl cellulose, or a combination thereof. 12. The coreless roll of any of items 1 to 8, wherein the nonionic polymer is a polyether polyol, preferably a polyether polyol selected from polyethylene glycol, polypropylene glycol, and mixtures thereof, more preferably polyethylene glycol, and wherein preferably at least 40%, more preferably at least 50%, more preferably at least 70% of the entire length of the continuous web of absorbent material in the machine direction comprises a coating composition comprising the polyether polyol. 13. The coreless roll of item 12, wherein the nonionic polymer has a number-average molecular weight of 800 to 250,000, preferably of 1,000 to 50,000, more preferably of 1,500 to 15,000, more preferably of 1,500 to 10,000, more preferably of 2,000 to 7,500, e.g., 2,500 to 4,000. 14. The coreless roll of any of items 1 to 13, wherein the coating composition comprises:

(a) at least 50 wt.-%, preferably at least 65 wt.-%, more preferably at least 80 wt.-% of the nonionic polymer;

(b) not more than 50 wt.-%, preferably not more than 35 wt.-%, more preferably not more than 20 wt.-% of further additives such as plasticizers, reinforcing agents, fragrance, and dyes;

each based on the total solids content of the coating composition.

15. The coreless roll of any of items 1 to 14, wherein the coating composition is applied in molten form or, after the addition of water, as an aqueous solution, wherein the aqueous solution preferably contains the nonionic polymer in an amount of at least 0.1 wt.-%, more preferably at least 0.5 wt.-% based on the total weight of the coating composition. 16. The coreless roll of any of items 1 to 15, wherein at least the last two, preferably at least the last three turns, preferably at least the last five turns, more preferably at least the last ten turns located at the second end of the continuous web of absorbent material comprise the coating composition. 17. The coreless roll of any of items 1 to 16, wherein the coating composition is applied such that, with respect to the length portion or length portions of the continuous web that comprise(s) the coating composition, the area covered by the coating composition is at least 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90% of the total area of said length portion(s). 18. The coreless roll of any of items 1 to 17, wherein if the coating composition has been applied continuously in the machine direction, the resulting coated portion starts at the second end and includes at least the last turn of the second end. 19. The coreless roll of any of items 1 to 17, wherein if the coating composition has been applied intermittently in machine direction, thereby providing two or more coated portions, (i) one coated portion includes at least the last turn of the second end and (ii) the amount of nonionic polymer applied to the half of the continuous web including the second end is preferably equal to or greater than the amount of nonionic polymer applied to the half of the continuous web including the first end. 20. The coreless roll of any of items 1 to 16, wherein the total amount of nonionic polymer is from 0.001 to 40 g/roll, preferably 0.005 to 10 g/roll, more preferably 0.005 to 5 g/roll, in particular 0.01 to 2 g/roll. 21. The coreless roll of any of items 1 to 20, wherein the web of absorbent material is composed of 1 tissue paper ply or 2 to 6, in particular 2 to 5 superposed tissue paper plies. 22. A coreless roll of an absorbent sheet product made of a spirally wound continuous web of absorbent material having a first end and a second end, the web of absorbent material being wound such as to define an axial hollow passageway centrally positioned relative to the coreless roll and extending from one edge to another edge of the coreless roll and such that the first end is located on the outer side of the roll and the second end is located at the axial hollow passageway;

wherein the coreless roll has a resiliency at 30 seconds of at least 75%, preferably at least 80%, more preferably at least 85%, even more preferably at least 90%, the resiliency at 30 seconds being determined as indicated in the description.

23. The coreless roll of claim 22, wherein the roll has a diameter of 50 to 500 mm, preferably of 80 to 200 mm, more preferably of 100 to 155 mm. 24. The coreless roll of item 22 or 23, which is defined as in one or more of items 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or 21. 25. The coreless roll of any of items 1 to 24 being in a compressed form. 26. The coreless roll of any of items 1 to 25, which is an absorbent product selected from the group consisting of napkins, towels, such as household towels, kitchen towels or hand towels, toilet papers, wipes, handkerchiefs, and facial tissues, wherein this absorbent product is preferably a toilet paper. 27. A manufacturing method for manufacturing a coreless roll of an absorbent sheet product comprising:

conveying a continuous web of absorbent material having a first end and a second end, which is preferably composed of 1 tissue paper ply or 2 to 6, in particular 2 to 5 superposed tissue paper plies;

optionally severing the continuous web of absorbent material substantially transversally to the machine direction to produce single but coherent sheets;

applying a coating composition as defined in any of items 1 to 20 to the continuous web;

spirally winding the continuous web of absorbent material so as to produce a log of web of absorbent material, the web of absorbent material being wound such as to define an axial hollow passageway centrally positioned relative to the log and extending from one edge to another edge of the log and such that the first end is located on the outer side of the log and the second end is located at the axial hollow passageway; and

cutting the log into multiple coreless rolls.

28. The manufacturing method of item 27, further comprising:

subjecting the coreless roll to compression in a direction perpendicular to the axial hollow passageway to produce a coreless roll in a compressed form.

29. The manufacturing method of item 27 or 28 wherein the coreless roll obtained by this method is defined as in one or more of items 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24. 30. Use of the coreless roll of any of items 1 to 26 as toilet paper, household towel, hand towel, kitchen towel, wipe, facial tissue, handkerchief or napkin.

Where the present description refers to “preferred” embodiments/features, combinations of these “preferred” embodiments/features shall also be deemed as disclosed as long as this combination of “preferred” embodiments/features is technically meaningful.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing showing a perspective view of a coreless roll according to an embodiment of the present invention.

FIG. 2 is a schematic drawing showing a lateral view of a coreless roll according to an embodiment of the present invention. The second end as represented in FIG. 2 has three turns.

FIG. 3 is a schematic drawing showing an unwound continuous web of absorbent material according to an embodiment of the present invention. The grey shading in FIG. 3 represents a coating composition that is applied to the last turn(s) located at the second end, and that is continuously applied to the continuous web of absorbent material. The combined coated portions of the continuous web of absorbent material (i.e., coated last turn(s) located at the second end and continuously coated web) is about 50% of the entire length of the web in the machine direction (MD).

FIG. 4 is a schematic drawing showing an unwound continuous web of absorbent material according to an embodiment of the present invention. The grey shading in FIG. 4 represents a coating composition that is applied to about 3 turns located at the second end, and that is intermittently applied to the continuous web of absorbent material. The combined coated portions of the continuous web of absorbent material (i.e., coated last turns located at the second end and intermittently coated web) is about 50% of the entire length of the web in the MD.

FIG. 5 is a schematic drawing of the last turns located at the second end of an unwound continuous web of absorbent material according to an embodiment of the present invention. The grey shading in FIG. 5 represents the coating composition which is applied continuously onto the last turns.

FIG. 6 is a schematic drawing of the coated area (length portion an unwound continuous web of absorbent material according to an embodiment of the present invention. The grey shading in FIG. 6 represents the coating composition which is applied intermittently as dots.

FIGS. 1 to 6 give a survey on the terminology used with respect to the coreless roll of the present invention. In FIGS. 1 to 6 the following reference numbers represent:

-   (1) Coreless roll -   (2) Spirally wound continuous web of absorbent material -   (3) Axial hollow passageway -   (4) Edge -   (5) First end -   (6) Second end -   (7) Coating composition -   (8) Perforation line

FIG. 7 is a schematic drawing showing a cross-section view of a converting machine (9) illustrating the manufacturing of coreless rolls according to one embodiment of the invention. FIG. 7 shows the application of the coating composition onto the continuous web of absorbent material by spraying.

FIG. 8 is a schematic drawing showing a cross-section view of a converting machine (9) illustrating the manufacturing of coreless rolls according to another embodiment of the invention. FIG. 8 shows the application of the coating composition onto the continuous web of absorbent material by roll-coating.

FIGS. 9a, 9b and 9c are schematic drawings of an apparatus (dynamometer) (39) and a shaft assembly (40)-(43) suitable for measuring the intersheet adhesion (delamination force) of a tissue paper roll (44) according to the present invention. The dimensions in FIGS. 9a-9c are given in mm.

DETAILED DESCRIPTION OF THE INVENTION 1. Coreless Roll

The coreless roll of an absorbent sheet product of the present invention according to one embodiment is made of a spirally wound continuous web of absorbent material having a first end and a second end.

The continuous web of absorbent material may be made of a base tissue paper which can be obtained by the Conventional Wet Press or the Through Air Drying (TAD) manufacturing method or other manufacturing methods. As used herein, “base (raw) tissue paper” (“tissue paper web”) means the one-ply base tissue as obtained from the tissue machine. The base tissue paper has a low basis weight, in the range of 8 to 60 g/m², preferably 10 to 30 g/m².

The term “ply”, as used herein, refers to the one or more plies of tissue paper in the final tissue paper product (e.g., toilet paper) as is/are obtained after processing (“converting”) one or more base tissue paper webs.

Based on the underlying compatibility of the production processes (wet forming), “tissue” production is counted among the papermaking techniques. The production of tissue is distinguished from paper production by its extremely low basis weight and its much higher tensile energy absorption index.

The tensile energy absorption index is arrived at from the tensile energy absorption in which the tensile energy absorption is related to the test sample volume before inspection (length, width, thickness of sample between the clamps before tensile load). Paper and tissue paper also differ in general with regard to the modulus of elasticity that characterizes the stress-strain properties of these planar products as a material parameter.

A tissue's high tensile energy absorption index results from outer or inner creping. The former is produced by compression of the paper web adhering to a dry cylinder as a result of the action of a crepe doctor or in the latter instance as a result of a difference in speed between two wires (“fabrics”). This causes the still moist, plastically deformable paper web to be internally broken up by compression and shearing, thereby rendering it more stretchable under load than uncreped paper. A high tensile energy absorption index can also be achieved by imparting to the tissue a 3D structure by means of the wires themselves. Most of the functional properties typical of tissue and tissue products result from the high tensile energy absorption index (see DIN EN 12625-4 and DIN EN 12625-5).

Typical properties of tissue paper include the ready ability to absorb tensile stress energy, their drapability, good textile-like flexibility, properties which are frequently referred to as bulk softness, a high surface softness, a high specific volume with a perceptible thickness, as well as high liquid absorbency and, depending on the application, a suitable wet and dry strength as well as an interesting visual appearance of the outer product surface. These properties allow tissue paper to be used, for example, as cleaning cloths (e.g., household towels), sanitary products (e.g., toilet paper, hand towels) and wipes (e.g., cosmetic wipes, facial tissues).

According to one embodiment of the present invention, the continuous web of absorbent material is preferably composed of 1 tissue paper ply or 2 to 5 superposed tissue paper plies.

The tissue paper can be produced from paper-making fibers according to “Conventional Processes” as in the manufacture of “Dry Crepe Tissue” or “Wet Crepe Tissue” or “Processes for Structured Tissue” such as the Through Air Drying (TAD) manufacturing method, the manufacture of uncreped through-air dried (UCTAD) tissue, or alternative manufacturing methods, e.g., the Advanced Tissue Molding System (ATMOS) of the company Voith, or Energy Efficient Technologically Advanced Drying eTAD of the company Georgia Pacific, or Structured Tissue Technology SST of the company Metso Paper. Hybrid processes like NTT (New textured Tissue) which are alterations of the conventional processes can be used, too.

The conventional dry crepe manufacturing method comprises:

pressing and drying the wet paper fibers as a sheet on a large-diameter, heated cylinder (also called Yankee dryer); and

subsequently detaching and creping the sheet of dried paper fibers by means of a metal blade applied against said cylinder, across its direction of rotation.

The creping operation creates undulations in the sheet across its direction of travel.

The creping operation increases the thickness of the sheet, and confers elasticity and gives touch (soft touch) properties to the sheet.

The TAD manufacturing method comprises:

molding the sheet of wet paper fibers on a fabric; and

subsequently drying the sheet, at least partly, by means of a current of hot air passing through it.

Subsequently, the dried sheet may be creped.

Further, in the manufacture of a tissue web (as preferred embodiment of the continuous web of absorbent material to be used), a process as described in PCT/EP2015/059326 (application date: 29 Apr. 2015; title: “Tissue paper comprising pulp fibers originating from Miscanthus and method for manufacturing the same”, incorporated by reference) can be used. Specifically, reference is made is to the description below according to item 3 and details of the TAD process (e.g., 3-D-shaped fabric, permeable drying cylinder, etc.) disclosed therein. The parameters described in this passage are also valid for the use of the ATMOS technology.

Once the tissue paper has been manufactured, a distinct manufacturing operation called converting operation is typically employed to form the tissue paper product (i.e., paper towels, toilet tissue rolls, bathroom tissues, wiping tissues, kitchen tissue rolls, handkerchiefs, etc.).

In one further embodiment of the continuous web of absorbent material the absorbent material is a “nonwoven material”. The term “nonwoven” is very common in the art and can be further defined in the manner described in ISO 9092:2011, also for the purpose of the present invention. Typical nonwoven manufacturing techniques include the air-laid technology, spun-laid technology, dry-laid technology, and wet-laid long fibers technology. The nonwoven web used according to this embodiment can be a single-ply or multi-ply web.

According to one aspect of this embodiment, the absorbent nonwoven-based web used in the coreless roll of the invention comprises cellulosic fibers. In this case, the content of the cellulosic fibers, based on the total weight of all fibers present in the nonwoven web, is at least 20 wt.-%, more preferably at least 50 wt.-%, for instance at least 80 wt.-%. The remaining fibers are in these cases non-cellulosic fibers such as synthetic fibers.

The aforementioned paper-making fibers (which can also be referred to as “cellulosic fibers”) can be produced from virgin and/or recycled paper pulp raw material. The cellulosic fibers which can be used in the invention typically contain as main structure-building component the long chain fibrous cellulose portion which is present in naturally occurring cellulose-containing cells, in particular those of lignified plants. Preferably, the fibers are isolated from lignified plants by digestion steps removing or reducing the content of lignin and other extractables and optional bleaching steps. The cellulosic fibers can also stem from non-wood sources such as annual plants.

Suitable cellulosic fibers which can be used may be of regenerated type (e.g., Lyocell), although the use of other types of pulps is preferred. The pulps employed can be a primary fibrous material (“virgin fibers”) or a secondary fibrous material (recycled pulps). The pulp can stem from lignin-free or low lignin sources, such as cotton linters, esparto (alfa) grass, bagasse (e.g., cereal straw, rice straw, bamboo, or hemp), kemp fibers, Miscanthus grass fibers, or flax (also referred to as “non-wood fibers” in the description and the claims). Preferably the pulp is produced from ligno-cellulosic material, such as softwood (which typically originates from conifers) or hardwood (typically from deciduous trees).

It is possible to use “chemical pulps” or “mechanical pulps”, whereby the use of chemical pulps may be preferred in one embodiment.

“Chemical pulps”, as used herein, are, according to DIN 6730, fibrous materials obtained from plant raw materials of which most non-cellulosic components have been removed by chemical pulping without substantial mechanical post treatment. “Mechanical pulp”, as used herein, is the general term for fibrous material made of wood entirely or almost entirely by mechanical means, optionally at increased temperatures. Mechanical pulp can be subdivided into the purely mechanical pulps (groundwood pulp and refined mechanical pulp) as well as mechanical pulps subjected to chemical pre-treatment, such as chemo-mechanical pulp (CMP), or chemo-thermo mechanical pulp (CTMP).

Referring to FIGS. 1 and 2, the continuous web of absorbent material (2) is spirally wound such as to define an axial hollow passageway (3) centrally positioned relative to the roll (1), and which extends from one edge (4) to the other edge (4) of the roll. As used herein, “axial hollow passageway” means a tubular opening that extends through the roll along its central axis. The axial hollow passageway enables the end user to mount the roll on the spindle of a roll holder. When the roll is mounted on the spindle of a roll holder, the absorbent material is dispensed from the first end (located at the outside of the roll) while the roll is allowed to freely rotate about its central axis. The axial hollow passageway has a diameter of from 10 mm to 70 mm, preferably from 20 to 50 mm.

In the present invention according to one embodiment, the axial hollow passageway (3) extends from one edge (4) to the other edge (4) of the coreless roll. The coreless roll of the present invention has a cylinder-shaped circumferential surface and opposite flat ends (i.e., edges), which are formed when the log roll is cut into multiple rolls at the end of the winding process. As used herein, “edge” means the flat portion which is located on one side of the roll perpendicular to its center axis.

In the present invention according to one embodiment, the continuous web of absorbent material (2) has a first end (5) and a second end (6). The first end (5) is located at the outside of the roll and the second end (6) is located at the axial hollow passageway (3). Hence, the continuous web of absorbent material consists, in the machine direction, of the first end and the second end and a middle portion located between these ends. The combined lengths of the first end, the second end and the middle portion define the entire length of the continuous web of absorbent material which forms one roll. In the coreless roll of the present invention, the continuous web of absorbent material comprises a coating composition specified in this application.

In the present invention according to one embodiment, the spirally wound continuous web of absorbent material has a (volumetric mass) density of from 50 to 140 mg/cm³, preferably 55 to 135 mg/cm³, more preferably 60 to 130 mg/cm³, more preferably 65 to 125 mg/cm³, more preferably of 70 to 120 mg/cm³, more preferably 80 to 110 mg/cm³, for instance 80 to 100 mg/cm³. The desired density can for instance be achieved by adjusting the bulk (cm³/g) of the continuous web of absorbent material and/or the winding force (strain) of the continuous web during the winding process. A greater winding force has the effect that a greater number of sheets can be accommodated in a roll of the same diameter as also illustrated by the present examples. When the continuous web of absorbent material constituting the roll is tightly wound (e.g., due to a higher strain applied in the winding process) and/or displays fairly low bulk values, the produced roll exhibits a high density, i.e., a high mass of absorbent material per unit volume. If the density of the produced roll exceeds 140 mg/cm³, the resiliency properties may not be fully developed. Furthermore, at higher density values the coreless roll may become relatively stiff and can no longer be compressed to the desired extent, e.g., for storage purposes.

Conversely, when the continuous web of absorbent material constituting the roll is relatively loosely wound (e.g., due to lower strain applied in the winding process) and/or displays fairly high bulk values, the produced roll exhibits a low density, i.e., a low mass of absorbent material per unit volume. However, a density of less than 50 mg/cm³ is not desired due to the increased risk of blockage of the rewinding unit when the continuous web is run at a speed adequate for industrial manufacturing, e.g., 10 m/s.

According to the present invention according to one embodiment, a coating composition is applied to the continuous web such that at least the last turn located at the second end (6) of the web comprises the same. As used herein, “turn” means one circumvolution of the spirally wound continuous web about the axial hollow passageway (3). FIG. 2 shows for instance the last three turns located at the second end (6) of the web. The coating composition may be applied to the web such that at least the two last turns, more preferably at least the three last turns, more preferably at least the last four turns, more preferably at least the last five turns, more preferably at least the last ten turns located at the second end comprise the coating composition.

In the present invention according to one embodiment, a coating composition is continuously or intermittently applied to the continuous web of absorbent material Furthermore, the continuous web of absorbent material such that at least 20% of the entire length of the continuous web in the machine direction comprise the coating composition.

The web length proportion in the machine direction (“at least 20% of the entire web length”), as used herein, refers to the total length of portions of the continuous web in the machine direction as coated by the non-ionic polymer comprising oxygen and/or nitrogen atoms (“first polymer”) with respect to the entire (total) length of the continuous web in the machine direction. It may include the last turn(s) located at the second end. There is no particular limitation as to the distribution of the coating composition comprising the first polymer with regard to the entire length of the continuous web, provided that at least 20% of the entire length of the continuous web in the machine direction comprises this coating composition. Optionally, the same coating composition is applied to the last turn(s) located at the second end and to the continuous web.

In one embodiment, the coating composition(s) is/are applied to the continuous web such that preferably at least 25%, at least 30%, at least 35%, at least 40%, at least 50%, more preferably at least 70%, more preferably at least 80%, for instance at least 90% of the entire length of the web in the machine direction comprises the coating composition comprising the first polymer. In one embodiment of the present invention, a coating composition is applied over the entire length of the continuous web in the machine direction, i.e., the coating composition is applied continuously in the machine direction from the first end (5) located at the outer side of the roll to the second end (6) located at the axial hollow passageway (3).

For the avoidance of doubt, these percentage values apply to the coating composition comprising a non-ionic polymer including oxygen and/or nitrogen atoms (also referred to as “first polymer”) only. In the event that at the second end of the continuous web at least the last turn comprises a different coating with an ionic polymer including oxygen and/or nitrogen atoms (also referred to as “second polymer”) the portions of the continuous web carrying the coating with the second polymer are not considered for determining the above percentage values.

Referring to the embodiment of FIG. 3, the continuous web of absorbent material has a first end (5) and a second end (6), wherein the last turns located at the second end (i.e., the web end located at the axial hollow passageway) comprise a coating composition and the continuous web comprises a coating composition that is continuously applied in the machine direction. If the same coating composition comprising the “first polymer” is used, the continuously coated portion which includes the last turn(s) located at the second end defines the coated length portion (in %) based on the entire length of the continuous web (i.e., combined lengths of the first end, the second end and the middle portion which define the entire length of the continuous web of absorbent material forming one individual roll).

Referring to the embodiment of FIG. 4, the continuous web of absorbent material has a first end (5) and a second end (6), wherein the last turns located at the second end (i.e., the web end located at the axial hollow passageway) comprise a coating composition and the continuous web comprises a coating composition that is intermittently applied in the machine direction. If the same coating composition comprising the “first polymer” is used, the combined lengths of the coated last turn(s) located at the second end and the intermittently coated portions define the coated length portion (in %) based on the entire length of the continuous web.

In one embodiment, the polymer including oxygen and/or nitrogen atoms (“second polymer”) comprised in the coating composition, which is applied to the last turn(s) located at the second end, is a nonionic polymer and preferably said coating composition is the same as that applied over at least 20% of the entire length of the continuous web of absorbent material.

In one further embodiment of the present invention, the coating composition is applied to the continuous web of absorbent material such that the maximum intersheet adhesion (delamination force) between the coated portions of the continuous web and the portions of the continuous web being in contact therewith is of from 0.3 to 1.7N, preferably 0.4 to 1.5N, e.g., 0.5 to 1.2N. The intersheet adhesion can be determined as indicated in the experimental section.

In one embodiment, the present invention relates to a coreless roll of an absorbent sheet product made of a spirally wound continuous web of absorbent material having a first end and a second end, the web of absorbent material being wound such as to define an axial hollow passageway centrally positioned relative to the coreless roll and extending from one edge to another edge of the coreless roll and such that the first end is located on the outer side of the roll and the second end is located at the axial hollow passageway;

wherein the coreless roll has a resiliency at 30 seconds of at least 75%, preferably at least 80%, more preferably at least 85%, even more preferably at least 90%, the resiliency at 30 seconds being determined as indicated in the experimental section.

To the best knowledge of the inventors, coreless rolls with such superior resiliency properties have not been produced or described before. The inventors have surprisingly found that such products can be provided by applying suitably selected coating compositions/polymers to a certain percentage of the entire length of the absorbent web and by using the coated web for preparing rolls having a suitably selected density as described in further detail in the description and the appended claims. One advantage of these coreless rolls lies in the improved optical appearance of the roll after having been compressed and/or subjected to deformation forces. The greater the resiliency value is, the further the axial hollow passageway will reopen after the deformation/compression force has been released. Coreless rolls with the claimed resiliency values will have substantially the same appearance to the customer before and after compression and do not create the perception of a low-quality product.

In one embodiment, the coreless roll of the present invention is provided in a compressed form. As used herein, “compressed form” means a form in which the roll cross section has an oval shape. When the roll is in the compressed form, the axial hollow passageway adopts a narrow oval shape (with full compression the shape of a narrow oval slit) and may no longer able to receive the spindle of a roll holder. As a result, the roll requires less space and storage and transport costs can be reduced. Due to the superior resiliency values, the coreless roll of the present invention is able to automatically return from the compressed form (oval) to a substantially uncompressed form (cylindrical or only slightly oval) even if no pressure is applied along the longer side (diameter) of the oval-shaped roll, i.e., perpendicular to the axis of the roll.

2. Coating Composition(s) Used for Coreless Roll

In the present invention according to one embodiment, a coating composition comprising a (preferably nonionic) polymer including oxygen and/or nitrogen atoms is applied to at least the last turn located at the second end of the continuous web, and a coating composition comprising a nonionic polymer, including oxygen and/or nitrogen atoms, is applied to at least 20% of the entire length of the continuous web in the machine direction.

Accordingly, in the present invention, a distinction is made between the non-ionic polymer including oxygen and/or nitrogen atoms applied to at least 20% of the entire length of the continuous web (also referred to as “first polymer”) and the polymer including oxygen and/or nitrogen atoms applied to at least the last turn located at the second end (also referred to as “second polymer”), which can be ionic but is preferably non-ionic and more preferably the same polymer as used as first polymer.

The polymers usable in the present invention are described in more detail in sections 2.1 and 2.2 below.

If the first and second polymers are identical, it is also preferred in one embodiment that at least the last turn located at the second end comprises the same coating composition as applied over at least 20% of the entire length of the continuous web. For this exemplary embodiment of the present invention, the following applies.

The coating composition usable in the present invention preferably comprises in one embodiment:

(a) at least 50 wt.-% of said nonionic polymer, preferably at least 65 wt.-%, more preferably at least 80 wt.-%, more preferably at least 85 wt.-%, more preferably at least 90 wt.-%, more preferably at least 95 wt.-%;

(b) not more than 50 wt.-%, preferably not more than 35 wt.-%, preferably not more than 20 wt.-%, more preferably not more than 15 wt.-%, more preferably not more than 10 wt.-%, more preferably not more than 5 wt.-% of further additives such as plasticizers, reinforcing agents, fragrance, dyes, etc.;

each based on the total solids content of the coating composition.

In one further embodiment, the coating composition consists of these ingredients in the stated amounts.

In one embodiment, the coating composition consists of a nonionic polymer which preferably has a melting point greater than 20° C., more preferably greater than 30° C., more preferably greater than 40° C. as determined by a dynamic mechanical analyzer (DMA, material pocket with single cantilever bending geometry) based on the tan δ response, the measurement being run from −120° C. to 75° C., with a gradient of 3° C. per minute and a frequency of 1.0 Hz. One example for such non-ionic polymers are the polyether polyols described in more detail below.

The coating composition can be applied to the continuous web of absorbent material (in particular its “second end”) in a molten state after heating to a temperature at or above the specified melting point, e.g., by spraying, controlled fiberization, roll-coating, slot-die application or any other suitable application method known in the art.

In one embodiment, the coating composition can be applied as an aqueous solution. This means that water is added to the coating composition and used as solvent for the nonionic polymer and the further additives, if present. The aqueous solution of the coating composition preferably contains the nonionic polymer in a total amount of at least 0.1 wt.-%, preferably at least 0.5 wt.-%, more preferably at least 1 wt.-% based on the total weight of the aqueous solution. Further additives such as plasticizers, reinforcing agents, fragrance, dyes, etc., may also be present. In this case, the contents thereof described above in connection with component (b) can also be employed (but refer to the total dry content of the aqueous solution).

Water may be present in an amount which is greater than 50 wt.-%, and more preferably in an amount greater than 65 wt.-%, more preferably greater than 80 wt.-%, based on the total weight of the aqueous solution.

This aqueous solution of the coating composition can be applied as it is, preferably at room temperature, to the continuous web of absorbent material, e.g., by spraying, controlled fiberization, roll-coating, or any other suitable application method known in the art. After the application of the aqueous solution, the continuous web of absorbent material can be dried, for instance by longer storage at ambient conditions or other suitable techniques known in the art. Depending on the water content, such drying step may also be unnecessary since the web of absorbent material itself will remove water from the aqueous solution, thereby leaving behind the coating composition on the web.

In one embodiment, the coating composition is applied to the last turn(s) located at the second end and/or to the continuous web as an aqueous solution and has an ionic demand of −1000 to +100 μeq/g, preferably of −500 to +50 μeq/g, more preferably of −50 to 0 μeq/g. The expression “ionic demand”, as used herein, refers to the total surface charges of all dissolved and undissolved substances present in the aqueous solution. The ionic demand can be measured by techniques known in the art such as polyelectrolyte titration. A suitable apparatus for the measurement of the ionic demand is the Particle Charge Detector PCD 03 available from BTG Mütek GmbH, Germany.

In the present invention according to one embodiment, the coating composition is applied onto at least one of the two sides of the continuous web, i.e., the upper and/or the lower side of the continuous longitudinal web. “Upper” side, as used herein, means the side of the continuous web that is oriented towards the outside of the roll when the web is spirally wound. In one preferred embodiment, the coating composition is applied onto the “lower side”, i.e., the side oriented towards the axial hollow passageway. If however only a fairly low number of turns located at the second end, for instance one or two (e.g., up to three turns) comprise the (preferably non-ionic) polymer including oxygen and/or nitrogen atoms, it may be advantageous to apply the coating composition to the “upper side” in order to make sure that the upper side of the individual turns sufficiently adheres to the lower side of the next turn.

The coating composition may be applied onto the continuous web before it is spirally wound to produce the roll. As a result of winding, the coating composition is applied circumferentially with respect to the axial hollow passageway. In the present invention according to one embodiment, the coating composition may be applied onto the web such that, with respect to the total length of the web (i.e., the length portion or portions carrying the resulting coating), at least 20%, preferably at least 25%, preferably at least 30%, preferably at least 35%, preferably at least 40%, preferably at least 50%, more preferably at least 70%, and in particular at least 80% are coated.

In the present invention according to one embodiment, the coating composition may be applied such that, with respect to the length portion(s) of the continuous web that comprises the coating composition, the area coated by the coating composition (be it a full coating or a partial coating) covers at least 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90% of the total area of said length portion(s).

The coating composition can be applied onto the continuous web to provide a full or partial coating.

“Full coating”, as used herein, means a coating that is applied continuously in the machine and the axial (cross) direction. This full coating may include the second end of the web (see, e.g., FIG. 5).

In accordance with one embodiment of the present invention, the coating composition may be applied such as to provide a full coating on the coated length portion of the web. This means that, with respect to the length portion of the continuous web that comprises the coating composition, the area coated by the coating composition is 100%.

Moreover, such full coating may include the last turn(s) of the second end of the continuous web. In other words, if the same coating composition is used for coating the last turn(s) at the second end as well as the desired length portion (e.g., 20% or 40%) of the continuous web, the remaining portion (80% or 60%) remains uncoated. Further, if the coating composition is applied continuously in machine direction, the resulting coated length portion may start at the second end and include at least the last turn of the second end.

A partial coating occurs for instance if the coating is applied to the web intermittently in the machine and/or axial direction. The coating composition can be applied onto the web so as to form predetermined coating patterns. The applied pattern of coating composition may be symmetrically and centrally arranged with respect to the symmetry axis running parallel to the machine direction (which divides the absorbent web in two equal hypothetical halves). There is no particular limitation to the predetermined coating pattern. The partial coating may form coherent (e.g., stripes, lines, or waves) or separate deposits (e.g., dots, squares, circles or any other geometric shape).

In one embodiment, the coating composition is applied continuously in the machine direction but intermittently in the axial direction, i.e., it does not cover the entire (axial) cross section. This can for instance be achieved by applying a wide stripe (“band”) of coating composition over the desired length of the entire continuous web. This wide stripe of coating composition is preferably symmetrically and centrally arranged with respect to symmetry axis running parallel to the machine direction. As described above, the area coated by this wide stripe of coating composition preferably covers at least 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90% of the total area of the coated length portion(s).

In one further embodiment of a partial coating, the coating is applied continuously in the axial (cross) direction, but intermittently in the machine direction, e.g., in the form of parallel stripes running in the axial direction, i.e., from one edge of the roll to the other edge, or in the form of several coated areas alternating with uncoated areas as shown for instance in FIG. 4. In order to determine for this embodiment whether it meets the requirement of the present invention according to one embodiment, the total length proportion of coated areas needs to be calculated. If for instance the total length of the continuous web is 20 m and altogether 4 portions each having a length of 2 m (one of these portions including the last turn(s) located at the second end) have been coated (with a coating composition comprising a non-ionic polymer including oxygen and/or nitrogen atoms, i.e., the first polymer), altogether 40% of the entire length of the continuous web comprise the coating composition.

If the coating composition has been applied intermittently in machine direction, thereby providing two or more coated portions, it is preferred according to one embodiment that (i) one coated portion includes at least the last turn of the second end. Further, as to the distribution of the coating composition over the length of the continuous web, it is preferred according to one embodiment that (ii) the total amount of nonionic polymer applied to the half of the continuous web including the second end is equal to or greater than the total amount of nonionic polymer applied to the half of the continuous web including the first end. In the latter case (“greater than”) the difference may for instance be at least 10%, at least 20%, or at least 50%. According to one aspect of the invention, condition (ii) applies in particular to those embodiments wherein not essentially the full length of the continuous web comprises the coating compositions but only a part thereof, e.g., 20 to 80%.

In one further embodiment of the partial coating, the coating is applied intermittently in the machine and axial (cross) direction, e.g., in the form of parallel stripes crossing each other. Alternatively, the coating is applied intermittently in the form of dots as shown in FIG. 6. The dots can form a regular or irregular pattern, as results, e.g., from spraying, fiberizing or roll-coating. Also for this embodiment it is preferred that the area coated by the partial coating covers at least 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90% of the total area of the coated length portion(s). FIG. 6 for instance shows a partial coating which covers essentially 100% of the length portion of the continuous web comprising the coating composition.

One function of the non-ionic polymer (“first polymer”) applied to at least 20% of the entire length of the continuous web is to provide the same with resiliency. At the same time, if applied to at least the last turn of the second end, the first polymer is also effective in adhering the absorbent web material of one turn to the web material of the adjacent turn(s). This ensures that the second end of the coreless roll is stabilized and prevents the last turn(s) from peeling off and collapsing.

Since this function does not necessarily require the use of a non-ionic polymer, it is within the scope of the present invention that at least the last turn located at the second end of the continuous web comprises a coating composition which comprise an ionic (anionic or cationic) or nonionic polymer including oxygen and/or nitrogen atoms (“second polymer”).

2.1. Polymer Comprising Oxygen and/or Nitrogen Atoms (“Second Polymer”)

The “second polymer” can be selected from ionic (anionic or cationic) polymers and non-ionic polymers.

A) In one embodiment, the coating composition applied to at least the last turn located at the second end comprises an ionic polymer including oxygen and/or nitrogen atoms. This ionic polymer can be selected from known adhesive polymers with low tack suitable for the lamination of paper webs. The adhesive polymer can be synthetic or of natural origin. Suitable embodiments comprise polysaccharide-based ionic polymers, for instance polysaccharide derivatives (e.g., cellulose derivatives) with carboxy functional groups, such as carboxymethyl cellulose (CMC) or gum arabic. As coating composition comprising an ionic polymer commercially available, preferably water-based adhesives can be used. These may also comprise other additives.

For embodiment (A), the coating composition may be applied to less than five turns, more preferably less than three turns, counting from and including the last turn located at the second end. Furthermore, the total amount of coating composition (solid content) per roll may be less than 0.05 g, preferably less than 0.03 g.

(B) If a nonionic polymer is used for coating at least the last turn located at the second end, this non-ionic polymer may be the same as used for coating at least 20% of the entire length of the continuous web. In other words, in this embodiment, the second polymer and the first polymer are identical and preferably the coating composition applied to at least 20% of the entire length of the continuous web is identical to the coating composition used for coating at least the last turn located at the second end. 2.2 Nonionic Polymer Comprising Oxygen and/or Nitrogen Atoms (“First Polymer”)

In the present invention according to one embodiment, a coating composition comprising a (preferably nonionic) polymer including oxygen and/or nitrogen atoms is applied to at least the last turn located at the second end of the continuous web of absorbent material and a coating composition comprising a nonionic polymer including oxygen and/or nitrogen atoms is applied to at least 20% of the entire length of the continuous web in the machine direction. If used in a coreless roll of suitable density, the application of the coating composition comprising the nonionic polymer (“first polymer”) to at least 20% of the entire length of the absorbent web surprisingly leads to superior resiliency (and thus also appropriate flexibility and elasticity) but also sufficient stiffness (and thus also resistance to collapsing) and a suitable delamination force. These effects can be further enhanced if the first polymer is also used for coating at least the last turn located at the second end of the continuous web. In accordance with the present invention the preferred polymers to be used can be described as follows.

Polymers can be divided into two categories, namely ionic polymers and nonionic polymers. Polymers of the ionic type contain substituents that are electrically charged, whereas polymers of the nonionic type carry electrically neutral substituents. The polymers used in the present invention may be of the nonionic type.

The nonionic polymers used herein include oxygen and/or nitrogen atoms. Without being bond to any theory, it is believed that the nonionic polymers used herein promote adequate electrostatic interactions, in particular the formation of intermolecular hydrogen bonds, e.g., hydrogen bonds between nonionic polymer and absorbent material (for instance cellulosic fibers) as well as hydrogen bonds between individual molecules of nonionic polymer, and intramolecular hydrogen bonds, e.g., electrostatic interactions occurring between oxygen and/or nitrogen atoms and hydrogen atoms within different parts of one polymer molecule. Moreover, it is believed that the aforementioned interactions give rise to adequate stiffness and resiliency properties whilst, at the same time, providing a suitable degree of intersheet adhesion (a degree of electrostatic interactions adequate to promote reversible intersheet adhesion).

In one embodiment, the nonionic polymer used herein comprises at least one repeating unit comprising one or more oxygen and/or one or more nitrogen atoms, for instance 1 to 5 oxygen and/or 1 to 5 nitrogen atoms, in particular 1 to 3 oxygen and/or 1 to 3 nitrogen atoms, e.g., 1 to 3 oxygen atoms. In accordance with the common understanding of this term, “repeating unit” (also sometimes referred to as “repeat unit” or “monomer unit”) refers in particular to one or more parts (units) of the polymer whose repetition produces the complete polymer chain by linking the repeating units together successively along the chain, with the exception of possible structural modifications at the end groups.

In one further embodiment, the nonionic polymer comprises at least one repeating unit comprising one or more ether oxygen atoms and/or one or more hydroxyl groups.

In one embodiment, on average at least 50%, preferably at least 80% of all repeating units constituting the nonionic polymer (and thus the complete polymer chain with the exception of the end groups) comprise one or more oxygen and/or one or more nitrogen atoms, preferably one or more ether oxygen atoms and/or one or more hydroxyl groups and/or one or more amino groups, more preferably one or more ether groups and/or one or more hydroxyl groups.

In one embodiment, the nonionic polymer exhibits a solubility in water at 25° C. of at least 40 g/l, preferably 200 g/l, in particular 500 g/l. The solubility of the nonionic polymer in water ensures that the absorbent sheet product of the present invention (in particular toilet paper, etc.) has good flushability. Due to the fairly high solubility of the nonionic polymer it dissolves upon contact with water in the sewage system, or at least quickly forms a dispersion. As a result, sewage systems can be effectively prevented from clogging up. For other embodiments of the coreless roll which are normally not disposed via the sewage system, such as napkins, towels, e.g., household towels, kitchen towels or hand towels, toilet papers, wipes and facial tissues, this feature is not required but preferred.

The use of biodegradable non-ionic polymers is also preferred according to one embodiment.

In the present invention according to one embodiment, the amount of nonionic polymer in the coating composition is set such that a total amount of from 0.001 to 40 g/roll, preferably 0.005 to 10 g/roll, more preferably 0.005 to 5 g/roll, more preferably 0.01 to 2 g/roll, more preferably 0.1 to 1.5 g/roll it applied to the web. The amount of nonionic polymer, as used herein, is to be understood as the total amount of nonionic polymer (first polymer”) applied to the continuous web. When the amount of nonionic polymer applied to the continuous web is less than 0.001 g/roll, the desired properties in terms of stiffness and resistance to collapsing may not be fully developed. Conversely, when the amount of nonionic polymer applied to the continuous web is greater than 40 g/roll, the roll exhibits a high stiffness and resistance to collapsing, but manufacturing costs may become high.

In one further embodiment, the nonionic polymer used herein is a nonionic cellulose ether, which can be described as follows.

Cellulose ethers are polymers derived from cellulose, which are formed by substituting (fully or partially) the hydroxyl groups of cellulose. The use of one etherification agent (alkylating agent) in the substitution process results in a simple cellulose ether, whereas using different kinds of agents leads to mixed cellulose ethers (mixed ethers). The extent of substitution is described as the degree of substitution (DS) defined as the average number of hydroxyl groups substituted per anhydroglucose unit. The DS can vary between >0 and 3. If an etherification (alkylating) agent such as an alkylene oxide etherification agent is used, a new hydroxyl group can be generated, and can further react to give oligomeric chains. In this case, the extent of substitution is described as the molar substitution (MS) defined as the average number of moles of etherification agent combined per mole of anhydroglucose unit.

The degree of substitution (DS) and the molar substitution (MS) of (ionic or nonionic) cellulose ethers can be determined by techniques known in the art, e.g., by ¹³C NMR or by the Zeisel gas chromatography (Zeisel-GC) method as described by Hodges et al. in Anal. Chem., 1979, 51(13), 2172-2176.

Cellulose ethers are divided into two categories, namely ionic cellulose ethers and nonionic cellulose ethers. Cellulose ethers of the ionic type, e.g., sodium carboxymethyl cellulose (CMC), contain substituents that are electrically charged, whereas cellulose ethers of the nonionic type, e.g., methyl cellulose, hydroxypropyl cellulose, etc., carry electrically neutral substituents. The cellulose ethers to be used in the present invention are of the nonionic type.

Without being bound to any theory, it is believed that nonionic cellulose ethers provide a fine-tuned degree of adhesion between the coating composition and the elongated absorbent material (continuous web). As a result, it is possible to achieve excellent stiffness and resistance to collapsing as well as sufficient flexibility and elasticity. Furthermore, the delamination force can be maintained in an acceptable range, and hence it is possible to use the elongated absorbent material on its whole length, i.e., up to the last sheet.

As used herein, the term “nonionic cellulose ether” is to be understood broadly and includes all types of cellulose ethers—e.g., alkyl cellulose ethers, hydroxyalkyl cellulose ethers, alkyl hydroxyalkyl cellulose ethers, and mixed ethers thereof—provided that they are nonionic.

In one embodiment, the nonionic cellulose ether has a number-average molecular weight of 1,000 to 2,000,000, e.g., 1,000 to 1,000,000, preferably of 2,000 to 800,000, e.g., 2,000 to 500,000, more preferably of 3,000 to 200,000, more preferably 5,000 to 100,000. The number-average molecular weight of the nonionic cellulose ether used in the present invention can be determined by techniques known in the art, such as Gel Permeation Chromatography (GPC).

In one further embodiment, the nonionic cellulose ether has a viscosity-average molecular weight of 5,000 to 2,000,000, preferably of 10,000 to 1,500,000, more preferably of 30,000 to 1,000,000. The viscosity-average molecular weight of the nonionic cellulose ether used in the present invention can be determined by techniques known in the art, such as viscometry.

In one further embodiment, the nonionic cellulose ether is an alkyl cellulose ether such as methyl cellulose or ethyl cellulose. As “alkyl cellulose ether” we understand a (nonionic) cellulose ether wherein some of the hydroxyl groups of cellulose (at least one hydroxyl group in one individual anhydroglucose unit) are substituted with an alkyl group, i.e., an linear or branched alkyl group having from 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms, more preferably from 1 to 6 carbon atoms, in particular a methyl group, an ethyl group or a propyl group. Furthermore, the expression “alkyl cellulose ether” is meant to encompass alkyl cellulose ethers such as methyl cellulose or ethyl cellulose as well as their mixed ethers such as hydroxyalkyl methyl celluloses, e.g., hydroxyethyl methyl cellulose.

In one embodiment, the nonionic cellulose ether is an alkyl cellulose ether selected from methyl cellulose (MC), mixed ethers of MC such as hydroxyethyl methyl cellulose (HEMC), hydroxypropyl methyl cellulose (HPMC) and hydroxybutyl methyl cellulose (HBMC), ethyl cellulose (EC), mixed ethers of EC such as hydroxyethyl ethyl cellulose (HEEC), hydroxypropyl ethyl cellulose (HPEC) and hydroxybutyl ethyl cellulose (HBEC). The alkyl cellulose ether may be MC, EC, or HPMC, more preferably MC or EC.

MC as used herein can have a DS of 1.4 to 2.4, preferably of 1.6 to 2.0. HEMC as preferably used herein can have a (methyl) DS of 1.3 to 2.2 and a (hydroxyalkyl) MS of 0.06 to 0.5. HPMC as preferably used herein can have a DS of 1.1 to 2.0 and a MS of 0.1 to 1.0. HBMC as preferably used herein typically has a DS greater than 1.9 and not more than 2.4 and a MS greater than 0.04 and not more than 0.6. EC as preferably used herein can have a (ethyl) DS of 1.0 to 2.5, preferably a DS of 1.1 to 1.5.

In another embodiment, the nonionic cellulose ether is a hydroxyalkyl cellulose ether such as hydroxyethyl cellulose or hydroxypropyl cellulose. As used herein, “hydroxyalkyl cellulose ether” means a (nonionic) cellulose ether, wherein some of the hydroxyl groups of cellulose are substituted with a hydroxyalkyl group, e.g., a linear or branched hydroxyalkyl group having from 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms, more preferably from 1 to 6 carbon atoms such as a (2-)hydroxypropyl group or a hydroxyethyl group.

In one embodiment, the nonionic cellulose ether is a hydroxyalkyl cellulose ether selected from hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC) and hydroxybutyl cellulose (HBC). The hydroxyalkyl cellulose ether may be HEC or HPC, more preferably HPC. HEC, as used herein, can have a MS of 0.1 to 3.6, preferably of 1.5 to 3.5. HPC, as used herein, can have a MS of 1.0 to 3.8, preferably of 2.0 to 3.6.

The definition of “nonionic cellulose ether” also includes a blend (combination) of at least two, e.g., 2, 3 or 4, different nonionic cellulose ethers, especially a blend of an alkyl cellulose ether and a hydroxyalkyl cellulose ether such as a blend of MC and HPC.

In one further embodiment, the coating composition includes one or more “nonionic cellulose ether” as the sole non-ionic polymer(s) and is in particular free of polyether polyol and/or free of other saccharides than the nonionic cellulose ether.

In one other embodiment, the nonionic polymer used herein is a polyether polyol, preferably a polyether polyol selected from polyethylene glycol, polypropylene glycol, and mixtures thereof, more preferably polyethylene glycol.

In one embodiment, the polymer has a number-average molecular weight of 800 to 250000, preferably of 1000 to 50000, more preferably of 1500 to 15000, more preferably of 1500 to 10000, more preferably of 2000 to 7500, e.g., 2500 to 4000.

In one embodiment, the polymer is polyethylene glycol having a number-average molecular weight of 800 to 250000, preferably of 1000 to 20000, more preferably of 1500 to 10000, more preferably of 2000 to 7500, more preferably of 2500 to 6500, even more preferably of 2500 to 4000.

The number-average molecular weight of the polymer used in the present invention can be determined by techniques known in the art, such as Gel Permeation Chromatography (GPC).

In another embodiment, the polymer used in the present invention is represented by the following formula (I):

wherein, in the above formula, n represents an integer having an average value of 10 to 5000, preferably of 10 to 2500, more preferably of 20 to 1000, more preferably of 30 to 200, more preferably of 50 to 150, or 50 to 100. Preferably, n represents an integer having an absolute value of 10 to 5000, preferably of 10 to 2500, more preferably of 20 to 1000, more preferably of 30 to 200, more preferably of 50 to 150, or 50 to 100.

2.3 Additives Plasticizer

The coating composition of the present invention may include a plasticizer, for instance a known plasticizer of an ester type. The plasticizer may contribute to the film-forming properties of the coating composition. It is selected such as to be compatible with the polymer described above. In one embodiment, the coating composition of the present invention is free of plasticizer.

One type of plasticizer may be used on its own or two or more types may be used in combination.

From the viewpoint of stability over time, the content of the plasticizer in the coating composition of the present invention is preferably no greater than 20 wt % of the total solids content concentration, more preferably no greater than 10 wt %, yet more preferably no greater than 5 wt %.

Strengthening Agent

The coating composition of the present invention may include a strengthening agent.

In one embodiment, the coating composition of the present invention is free of strengthening chemical additives, such as strength resins, for instance free of the water-soluble cationic or anionic polymers described below. When the coating composition includes a strengthening agent, a water-soluble cationic polymer, and/or a water soluble anionic polymer as known in the art can be used.

Other Additives

The composition of the present invention may comprise as appropriate various types of known additives as long as the effects of the present invention are not inhibited. Examples include a fragrance, a colorant, a surfactant, an anti-scaling agent, and an anti-bacterial agent as well as inorganic or organic fillers.

One type thereof may be used on its own or two or more types may be used in combination.

3. Absorbent Product Used for Coreless Roll

The coreless roll of the present invention has many applications in the field of sanitary or domestic absorbent products. In particular, the roll of the present invention can be an absorbent sheet product chosen among the group comprising napkins, towels such as kitchen towels or hand towels, toilet paper, wipes and facial tissues.

In the present invention according to one embodiment, the absorbent sheet product is made of a continuous web of absorbent material having a first end and a second end, which consists of at least one ply of base tissue paper with typical basis weight of from 8 to 60 g/m², preferably 10 to 30 g/m².

In one embodiment, the continuous web of absorbent material is a single ply web made of tissue paper or a multiple-ply web made of, e.g., 2 to 5 superposed tissue paper plies. To achieve a multiple-ply absorbent sheet product, the one-ply base tissues are combined in a converting step to the final ply count, which may be from, e.g., 2 to 5 depending on the targeted properties of the final product. The total basis weight of the resulting multiple-ply web preferably does not exceed 120 g/m², and more preferably is lower than 65 g/m², e.g., lower than 55 g/m².

In the present invention according to one embodiment, the second end of the continuous web is coated with the coating composition of the present invention (i.e., one comprising a polymer as described above) and spirally wound to achieve a roll of absorbent sheet product, such as a toilet paper roll. The coating composition can be applied onto the second end by using techniques known in the art. “Spraying” and “roll-coating” belong to these well-known techniques.

In the present invention according to one embodiment, the coating composition is applied onto at least one of the two sides of the continuous web, i.e., the upper and/or the lower side of the continuous longitudinal web, or between the base tissue paper plies forming the web.

When the web is a multiple-ply web, e.g., one having 2 to 5 superposed tissue paper plies, the coating composition can be applied onto one or both sides of one or more plies, e.g., onto all the plies. In one embodiment, the coating composition is applied onto one of the outer plies of the web, preferably onto the outer ply which is oriented towards the axial hollow passageway in the finished absorbent sheet product (i.e., the outer ply which is the one closest to the axial hollow passageway). The outer ply can be coated on one or both sides, preferably on its lower side, i.e., the side oriented towards the axial hollow passageway.

The absorbent sheet product of the present invention may be selected from napkins, towels such as kitchen towels or hand towels, toilet paper, wipes and facial tissues. As “toilet paper”, we understand a soft and strong base tissue paper, which is used to clean the posterior after using the toilet (sometimes also referred to as “bathroom tissue”).

The present invention also relates to the use of the coreless roll as toilet paper, household towel, kitchen towel, wipe, facial or napkin.

According to one embodiment, the absorbent sheet product is a toilet paper composed of 2 to 5 superposed tissue paper plies, e.g., 2 to 4 tissue paper plies, in which the coating composition is applied onto at least one outer ply of the continuous web, preferably on the lower side of the outer ply closest to the axial hollow passageway.

The dimensions of the coreless roll of the present invention are not limited and depend greatly on the targeted absorbent sheet product. An individual roll can for instance have a diameter (edge diameter) of from 5 cm to 50 cm, preferably from 8 cm to 20 cm (e.g., 100 mm to 155 mm). The axial hollow passageway can have a diameter of from 10 mm to 70 mm, preferably from 20 to 50 mm. The width of the roll (i.e., distance between one edge to another edge) can range from 60 mm to 800 mm, preferably from 70 mm to 400 mm, e.g., 80 mm to 150 mm.

The continuous web of absorbent material forming the absorbent sheet product preferably has a total length in the machine direction of from 1 m to 60 m, preferably from 1.5 m to 50 m, e.g., 2 m to 40 m. Optionally, the web can be partially severed in the machine direction such that it consists of consecutive single but coherent sheets. A single sheet can have a length (in the machine direction) of from 80 mm to 300 mm, e.g., 100 mm to 250 mm, especially of from 100 mm to 200 mm.

One further embodiment of the present invention can be described as follows:

A coreless roll of an absorbent sheet product made of a spirally wound continuous web of absorbent material having a first end and a second end, the web of absorbent material being wound such as to define an axial hollow passageway centrally positioned relative to the coreless roll and extending from one edge to another edge of the coreless roll and such that the first end is located on the outer side of the roll and the second end is located at the axial hollow passageway;

wherein the spirally wound continuous web of absorbent material has a density of from 60 to 130 mg/cm³, preferably of 70 to 120 mg/cm³;

wherein at least the last two turns located at the second end of the continuous web of absorbent material, preferably at least the last three turns, more preferably at least the last five turns, comprise a coating composition comprising a non-ionic cellulose ether (as non-ionic polymer), preferably alkyl cellulose ether such as methylcellulose or ethylcellulose, a hydroxyalkyl cellulose ether such as hydroxyethyl cellulose or hydroxypropyl cellulose, or a combination thereof; and

wherein at least 40%, e.g., 40 to 90%, or 50 to 80% of the entire length of the continuous web of absorbent material in the machine direction comprises said coating composition comprising said nonionic polymer; wherein:

-   -   a. the maximum intersheet adhesion between the coated portions         of the continuous web of absorbent material and the portions of         the continuous web being in contact therewith is preferably 0.4         to 1.5N, e.g., 0.5 to 1.2N, and/or     -   b. wherein the coating composition is preferably applied such         that, with respect to the length portion or length portions of         the continuous web comprising the coating composition, the area         covered by the coating composition covers preferably at least         50%, more preferably at least 60%, more preferably at least 70%,         more preferably at least 80%, more preferably at least 90% of         the total area of said length portion(s) and/or,     -   c. if the coating composition has been applied continuously in         machine direction, the resulting coated portion preferably         starts at the second end and includes at least the last turn of         the second end, and if the coating composition has been applied         intermittently in machine direction, thereby providing two or         more coated portions, (i) one coated portion includes at least         the last turn of the second end and (ii) the amount of nonionic         polymer applied to the half of the continuous web including the         second end is preferably equal to or greater than the amount of         nonionic polymer applied to the half of the continuous web         including the first end; and/or,     -   d. the amount of nonionic polymer is from 0.01 to 2 g/roll,         preferably 0.1 to 1.5 g/roll; and/or     -   e. the roll has a diameter (edge diameter) of from 8 cm to 20 cm         (e.g., 100 mm to 155 mm); and/or     -   f. the coating composition is free of polyether polyol and/or         free of other saccharides than the nonionic cellulose ether.

In one further embodiment, the coreless roll comprises all of the features (a.) to (f.). It should be noted that, where the present description teaches that features in the above feature combination can be replaced by broader or narrower ranges or broader or narrower terms/definitions, this results in further embodiments of the present invention.

4. Process for the Manufacture of Coreless Rolls and Absorbent Products

The present invention also relates to a process for the manufacture of a coreless roll as described before and below, the process comprising:

(A) conveying a continuous web of absorbent material having a first end and a second end, which is optionally composed of one tissue paper ply or 2 to 5 superposed tissue paper plies; (B) applying a coating composition comprising a (preferably nonionic) polymer including oxygen and/or nitrogen atoms to at least the last turn located at the second end of the continuous web, and applying a coating composition comprising a nonionic polymer including oxygen and/or nitrogen toms to at least 20% of the entire length of the continuous web in the machine direction; wherein the coating composition applied to the last turn(s) is preferably the same as that applied over at least 20% of the entire web length; (C) spirally winding the continuous web of absorbent material so as to produce a log of web of absorbent material, the web of absorbent material being wound such as to define an axial hollow passageway centrally positioned relative to the log and extending from one edge to another edge of the log and such that the first end is located on the outer side of the log and the second end is located at the axial hollow passageway; (D) optionally severing the continuous web of absorbent material substantially transversally to the machine direction to produce single but coherent sheets; and (E) cutting the log into multiple coreless rolls.

According to one embodiment of the present invention, the aforementioned process for the manufacture of a coreless roll further comprises:

(F) subjecting the coreless roll to compression in a direction perpendicular to the axial hollow passageway to produce a coreless roll in a compressed form.

The coreless roll of the present invention can be manufactured by using a commercially available converting machine. A suitable converting machine is available, for example, from the Paper Converting Machine Company (PCMC), Europe.

The description of the process below referring to machine modules/units is to be understood as an illustration of a machine suitable for manufacturing the roll of the present invention. The use of other kinds of machines/units known in the art is also possible.

In the present invention, referring to FIGS. 5 and 6, the process for the manufacture of a coreless roll comprises the steps of:

(A) Conveying a continuous web of absorbent material (19) having a first end and a second end.

The continuous web of absorbent material (19) to be used in the present invention according to one embodiment consists of one or more plies of base tissue paper having a basis weight of from 8 to 60 g/m², preferably from 10 to 30 g/m². The base tissue paper is typically provided as large parent rolls (15) and (16) having a width of from 1.80 m to 7 m as obtained from the tissue machine. The parent rolls (15) and (16) are mounted on the unwinding units (10) and (11) of converting machine (9). The number of parent rolls to be used corresponds to the ply count in the targeted absorbent sheet product. In FIGS. 5 and 6, two parent rolls (15) and (16) each providing one ply of bathroom tissue (18A) and (18B) are employed to produce a two-ply toilet paper roll (1).

The plies (18A) and (18B) are fed from the unwinding units (10) and (11) to an embossing unit (12), in which the plies are superposed and combined (associated) in order to produce a continuous web of absorbent material (19).

The embossing unit includes an engraved cylinder (20) and a mating rubber cylinder (21), both rotating in opposite directions, and optionally a glue dispenser (not shown). The engraved cylinder can be engraved with a microstructure pattern combining various embossing tips. The engraved cylinder can perform a simple- or a double-level engraving into the superposed plies.

The glue dispenser, if any, typically includes a vat (a reservoir for glue), an applicator cylinder and a dipping cylinder. The applicator cylinder abuts the superposed base tissue plies against the engraved cylinder. The dipping cylinder (not shown) picks up the adhesive in the vat and transfers the adhesive to the applicator cylinder (not shown). The applicator cylinder is arranged to exercise a determined pressure on the engraved cylinder at the distal area of protuberances of the embossed web. At said determined pressure, the adhesive crosses through the web and bonds the plies. The amount of adhesive used for ply bonding is preferably from 0.1 g/m² to 5.0 g/m², preferably from 0.2 g/m² to 1.0 g/m². An example of a suitable adhesive for ply bonding is Swift® tak 1004 available from H. B. Fuller, Europe.

The embossing step described above is used to combine plies of base tissue and, also, to emboss or micro-emboss at least one of the plies in order to generate esthetical effects or modify the thickness, the softness, or the suppleness of the resulting continuous web (19).

(B) Applying a coating composition to at least the last turn located at the second end of the continuous web and applying a coating composition over at least 20% of the entire length of the continuous web, wherein preferably the coating composition that is applied to the last turn(s) is the same as that applied over the at least 20% of the entire web length, so as to form a full or partial coating. The coating composition(s) is/are applied onto the continuous web (including the last turn(s)) by techniques known in the art. In the present invention, it is possible to use, amongst other techniques, spraying, controlled fiberization or roll-coating.

“Spraying”, as used herein, means that the coating composition(s) is/are applied onto the continuous web in the form of a dispersion of fine liquid droplets in a gas (i.e., a spray). A spray is typically formed by using a spray nozzle (spray gun) having a fluid passage that is acted upon by mechanical forces which atomize the liquid. The liquid droplets can have a size of from 1 μm to 1000 μm, e.g., 10 μm to 400 μm.

The converting machine (9) can be equipped with one or more spray guns (23A), e.g., 1 to 8 spray guns, which can be placed at any location of the converting line as long as this is meaningful in view of the desired results (coatings of second end). The spray gun(s) (23A) can be placed before the embossing unit (12) such that the coating composition (22) is applied, e.g., onto an outer ply or between the plies. Preferably, the spray gun(s) (23A) is/are placed between the cutting module (27) and the winding module (28) such that the coating composition(s) (22) is/are applied onto the lower side of an outer ply (as shown in FIG. 7).

The spraying system includes one or more spray gun(s) (23A), a vat (24) and pipes (25) feeding a coating composition (22) from the vat to the spray gun(s) (23A). Optionally, the spraying system is equipped with a heating system (e.g., heating jacket, heat guns, etc., not shown), which heats the coating composition in the vat (24), pipes (25) and/or gun(s) (23A) such that the composition is maintained in a liquid state during spraying. In particular, the heating system can heat the coating composition at a temperature above the melting point of the polymer used in the composition.

Spray guns suitable for spraying the coating composition(s) of the present invention are available, e.g., from Walther Spritz- and Lackiersysteme GmbH, Germany.

“Controlled fiberization”, as used herein, means that the coating composition(s) is/are applied onto the continuous web in the form of strands (thin filaments) having a controlled or random pattern, e.g., due to a swirling effects. The strands having a controlled or random pattern are typically formed by using a spray applicator which cooperates with a plurality of jets of air that fiberize the stream of coating composition leaving the spray nozzles. Spray applicator(s) suitable for applying the coating composition of the present invention are available, e.g., from ITW Dynatec® GmbH, Germany.

“Roll-coating”, as used herein, means that the coating composition(s) is/are directly applied onto the continuous web by means of an applicator roll. “Roll-to-roll coating” and “reverse-roll coating” belong to well-known techniques which can be used in the present invention. Referring to FIG. 8, the roll-coating system includes dipping cylinder and applicator cylinders (23B), a vat (24) and pipes (25) feeding the coating composition (22) from the vat to the dipping and applicator cylinders (23B). The roll-coating system includes optionally a heating system as described above (not shown). The roll-coating system can be placed at any location of the converting line as long as this is meaningful. The roll-coating system can be placed, for example, on the embossing unit in a manner that the applicator cylinder (23B) abuts against the engraved cylinder (20) or another cylinder (as shown in FIG. 8).

The spray gun(s) (23A) or the roll-coater (23B) can be adjusted to apply a continuous coating in the machine and axial direction or an intermittent coating (e.g., stripes, dots, etc.) in the machine and/or axial direction.

In some aspects of the present invention, the coating composition applied to at least the last turn located at the second end of the continuous web and the coating composition applied to at least 20% of the entire web length can be applied by using different techniques (if different coating compositions are used). For instance, the coating composition applied to the last turn(s) can be applied by roll-coating, whereas the coating composition applied over the at least 20% of the entire web length can be applied by spraying.

(C) Spirally winding the continuous web (19) so as to produce a log of web of absorbent material (34).

The continuous web (19) is fed from the embossing unit (12) to the rewinding unit (13) in which the web (19) is spirally wound so as to produce a log of web of absorbent material (34). The rewinding unit (13) includes a perforating module (26), a cutting module (27), a winding module (28) and an extraction module (33). The rewinding unit (13) winds the continuous web (19) into multiple logs (34).

The winding module (28) is arranged to wind the continuous web (19) so as to produce logs of web (34). The winding module (28) can be of the peripheral type (center winding) or the surface type (surface winding). The winding module includes a rolling surface (29), a first winding roller (30), a second winding roller (31), a third winding roller (32), and a temporary core supplier (not shown). The log is formed by winding the continuous web onto a temporary core (36) which maintains a well-defined axial hollow passageway. The temporary cores (36) are sequentially provided by the core supplier through the rolling surface (29) before the beginning of a new log production cycle. The temporary core (36) can be made, for example, of plastic or cardboard. A “fugitive glue” (pick-up glue) can be used to pick up the second end of the web (19) onto the temporary core (36) at the beginning of a new production cycle.

The log (34) is maintained in position during the winding by the first, second and third winding rollers (30), (31) and (32) rotating in surface contact with the log (34). One of the winding rollers (30), (31) and (32) may impose a rotation movement to the log (surface winding).

Once the desired log diameter (corresponding to a substantially defined web length or number of individual sheets) is reached, the continuous web (19) is cut. The produced log (34) is separated from the web (19) and subsequently the production of a new log begins.

The cutting unit (27) is arranged to cut the web according to regularly spaced cutting lines substantially transversally to the machine direction. The cutting of the web occurs at a transition phase, namely when a first log is finished at the end of a log production cycle, and before a second subsequent log starts being wound at the beginning of a new log production cycle.

The cutting lines (not shown) are lines in the axial direction made in the thickness of the web (19). Two consecutive cutting lines define the total web length forming one roll. The space between two consecutive cutting lines, i.e., the roll length, is determined depending on the target product. Typically, roll length and roll diameter are selected depending on, e.g., the number of plies forming the web, the basis weight of the individual plies, etc. An individual roll of absorbent sheet product can have a total web length in the machine direction of from 1 m to 60 m, preferably from 1.5 m to 50 m, e.g., 2 m to 40 m.

The produced log (34) is then provided to the extraction module (33), which is arranged to extract the temporary cores (36) from the log (34) after the winding of a log is completed. The temporary cores (36) may be recycled after extraction by the core supplier.

When the coating composition used in the process of the present invention is an aqueous solution as described hereinabove, the produced log can be subjected to drying. Subsequently, the produced log is separated from the web of absorbent material prior to extraction of the temporary core. The produced log can also be subjected to drying after extraction of the temporary core.

The produced log is preferably dried until the tissue paper forming the log contains an amount of water which does not exceed 10% of the total weight of the log, preferably 5% of the total weight of the log. For instance, the produced log can be dried by storing the log at room temperature (20° C. to 25° C.) and RH (relative humidity) of 10 to 60% for a period of 12 hours.

(D) Optionally severing the continuous web of absorbent material (19) substantially transversally to the machine direction to produce single but coherent sheets.

Before the continuous web (19) is spirally wound by the winding module (29) as described above, the web (19) reaches the perforating module (26), if any, which is arranged to provide the web (19) with regularly spaced perforation lines (8) substantially transversally to the machine direction, i.e., in the axial direction, so as to produce single but coherent sheets (as shown in FIGS. 3, 4 a and 4 b).

A perforation line (8) is a line in the axial direction made in the thickness of the web (19) and comprising alternating perforated segments and unperforated segments (i.e., two perforated segments being separated by one unperforated segment or vice-versa). Each unperforated segment forms an attachment area between two consecutive portions of the continuous web. Each perforated segment forms a detachment area between two consecutive portions of the continuous web. Considering the width of the individual roll, for example between 10 cm and 30 cm, the length of said unperforated/perforated segments can be from 1 mm to 15 mm, preferably from 4 mm to 10 mm. Other kinds of perforation lines are also possible as long as this is meaningful.

Two consecutive perforation lines (8) define the individual sheet length in the finished absorbent sheet product. The space between two consecutive perforation lines, i.e., the sheet length, is determined depending on the target product. A single sheet can have a length in the machine direction of from 80 mm to 300 mm, e.g., 100 mm to 250 mm. For example, a sheet of bathroom tissue can have a length of from 80 mm to 200 mm and a towel such as a household (kitchen) towel or hand towel can have a length of from 80 mm to 300 mm.

(E) Cutting the produced log (34) into multiple coreless rolls (1).

After winding, the log (34) is provided to the log cutting unit (14), in which the log (34) is cut parallel to the machine direction by multiple log saws (35) into multiple individual rolls (1). The multiple log saws (35) are regularly spaced in the axial direction such that the log (34) is cut into multiple individual rolls (1) having a determined width in the axial direction (i.e., distance from one edge to another edge). The width of an individual roll (1) is from 60 mm to 800 mm, preferably from 70 mm to 400 mm, e.g., 80 mm to 150 mm.

A control module (37) is coupled to the winding module (28), to the perforating module (26), to the cutting module (27) and to the spraying, fiberization or roll-coating system by means of an interface (38). The control module (37) controls the operation of the winding module (28), the perforating module (26) and the cutting module (27). In particular, the control module (37) controls the force applied to the continuous web during the winding process (thus allowing to achieve the desired roll density), activates the cutting module (27) to sever the web (19) at a transition phase between two consecutive logs, and controls the operation of the perforating module (26) out of transition phases.

In addition, the control module (37) controls the operation of the spraying, fiberization or roll-coating system, namely the appropriate application (spraying, fiberizing or roll coating) of the coating composition onto the second end of the continuous web (19). The appropriate application of the coating composition onto the second end can be controlled by sending, e.g., start/stop signals to the application system, which are determined based on the length of the target product and the machine parameters, e.g., running speed.

Various rollers (17) are appropriately positioned in order to control the path of the continuous web (19) along the converting machine (9), within and between the various units.

(F) Optionally, subjecting the roll to compression in a direction perpendicular to the axial hollow passageway to produce a coreless roll in a compressed (oval) form (not shown).

As used herein, “compression” means that a pressure is applied on the roll in a direction perpendicular to the axial hollow passageway so as to produce a roll having an oval cross section, which requires less storage space. Roll compression occurs preferably immediately after winding has been terminated. An appropriate device known in the art can be used to operate the compression. In the present invention, it is possible to use for example the two converging synchronically driven conveyor bands described in WO 95/13183, a pneumatic or hydraulic pressing plate, or other devices.

Thereafter, the individual coreless rolls (1) are packaged and prepared for shipping (not shown).

5. Examples

The following test methods were used to evaluate the absorbent materials, the polymers, and the coreless rolls produced.

5.1. Basis Weight

The basis weight was determined according to EN ISO 12625-6:2005, Tissue Paper and Tissue Products, Part 6: Determination of grammage.

5.2. Caliper

The measurement is made by a precision micrometer (precision 0.001 mm) according to a modified method based on EN ISO 12625-3:2014, Part 3. For this purpose, the distance created between a fixed reference plate and a parallel pressure foot is measured. The diameter of the pressure foot is 35.7±0.1 mm (10.0 cm² nominal area). The pressure applied is 2.0 kPa±0.1 kPa. The pressure foot is movable at a speed rate of 2.0±0.2 mm/s.

A usable apparatus is a thickness meter type L & W SE050 (available from Lorentzen & Wettre, Europe).

The tissue paper product to be measured is cut into pieces of 20×25 cm and conditioned in an atmosphere of 23° C., 50% RH (Relative Humidity) for at least 12 hours.

For the measurement, one sheet is placed beneath the pressure plate which is then lowered. The thickness value for the sheet is then read off 5 seconds after the pressure has been stabilized. The thickness measurement is then repeated nine times with further samples treated in the same manner.

The mean value of the 10 values obtained is taken as thickness of one sheet (“one-sheet caliper”) of the tissue paper product (e.g., a three-ply toilet paper) measured.

5.3. Number-Average Molecular Weight

The measurement is made by Gel Permeation Chromatography (GPC) using a PL-GPC 50 Integrated GPC/SEC System equipped with a PL aquagel-OH MIXED 8 μm column 7.5×300 mm (both available from Agilent Technologies, Europe). The GPC system was calibrated using a pullulan polysaccharide calibration kit available from Agilent Technologies (for methyl cellulose) or, depending on the polymer to be measured, with a suitable calibration kit such as hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxypropylmethyl cellulose calibration kits all available from American Polymer Standards Corporation or a PEG-10 EasiVial calibration kit available from Agilent Technologies.

A sample of the polymer to be measured was dissolved in water at a concentration of 2 mg/mL. The sample was injected (injection volume: 100 μL) and run at a flow rate of 1.0 mL/min and a temperature of 50° C. using an aqueous buffer solution 0.05M NaH₂PO₄, 0.25M NaCl pH 7 (for cellulose ethers) or water (for polyether polyols) as the eluent. The retention time (min) of the polymer was recorded as a peak. The number-average molecular weight of the polymer was determined by comparing the recorded retention time with that of standard (calibration) polymers.

5.4. Viscosity-Average Molecular Weight

The measurement can be conducted as follows by viscometry using an Ubbelodhe capillary viscometer equipped with a capillary having an internal diameter of 0.63 mm (both available from SI Analytics, Europe).

A sample solution (concentration C₁=10.0 g/l) of the polymer in water is prepared and transferred to the Ubbelodhe capillary viscometer. The viscometer is suspended in a thermostatic bath for 30 minutes at a temperature of (25±0.1)° C. The flow time (the time taken for the sample solution to flow between the two calibrated marks) is measured. The measurement is repeated five times and the mean value of the five values obtained is taken as flow time of the sample solution. The same measurement is reproduced with a sample of water (without cellulose ether). The Hagenbach-Couette corrections (as provided by SI Analytics) were subtracted from the measured flow times.

The relative viscosity z₁ of the sample of the cellulose ether can be calculated as follows:

$z_{1} = \frac{{Flow}\mspace{14mu} {time}\mspace{14mu} {of}\mspace{14mu} {the}\mspace{20mu} {samp1e}\mspace{20mu} {solution}}{{Flow}\mspace{14mu} {time}\mspace{14mu} {of}\mspace{14mu} {water}}$

The measurement is repeated using further sample solutions with concentrations C₂=5.0 g/l, C₃=3.33 g/l and C₄=2.5 g/l. The relative viscosities z₂, z₃ and z₄ are obtained.

The intrinsic viscosity n can be determined graphically by plotting the relative viscosity (y-axis) against the sample concentration (x-axis) and extrapolating the theoretical straight line backwards to zero concentration (the line cuts the y-axis at the height of the intrinsic viscosity).

The viscosity-average molecular weight Mv of the cellulose ether can be calculated using the Mark-Houwink-Sakurada equation (1) and the constants K and a of the cellulose ether as indicated in Brandrup, J., Immergut, E. H., Grulke, E. A., Polymer Handbook 4^(th) Edition, John Wiley & Sons, New York 1999 (hydroxyethyl cellulose: K=9.53.10⁻³ ml/g, α=0.87).

$\begin{matrix} {{\overset{\_}{M}\; v} = \sqrt[\alpha]{\frac{\eta}{K}}} & (1) \end{matrix}$

5.5. Density

The measurement of the roll densities were conducted as follows: the dimensions of the roll to be measured were taken including external diameter D, diameter of the axial hollow passageway d, and width h. The weight of the roll M was determined. The density of the roll δ was calculated using the following equation:

$\delta = \frac{4 \times M}{\pi \times {h\left( {D^{2} - d^{2}} \right)}}$

5.6. Axial Stiffness

The measurement was made by a vertical dynamometer equipped with a 2.5 kN cell. A usable apparatus is a dynamometer type ZwickiLine Z1.0 (available from Zwick Roell, Europe).

A roll was placed vertically between the pressure plates (on one of the two flat edges), and pressure was applied in a direction parallel to the axis of the hollow passageway. The roll was compressed between the plates at a constant speed of 60 mm/min. The compression force was measured and plotted against the displacement of the cell (y-axis: compression force; x-axis: cell displacement). The correlation between compression force and cell displacement was determined by linear regression in the elastic domain of the graph. The slope of the linear regression line was taken as the axial stiffness of the roll.

The measurement was repeated four times with further samples (toilet paper rolls from the same production batch), and the mean value of the five values obtained was taken as the axial stiffness K_(ax) of the roll.

5.7. Radial Stiffness

The measurement is made by a vertical dynamometer (Zwickiline Z1.0) equipped with a 200N cell.

A roll was placed horizontally between the pressure plates (on the round edge), and pressure was applied in a direction perpendicular to the axis of the hollow passageway. The roll was compressed between the plates at a constant speed of 60 mm/min. The compression force was measured and plotted against the displacement of the cell (y-axis: compression force; x-axis: cell displacement). The correlation between compression force and cell displacement was determined by linear regression in the elastic domain of the. The slope of the linear regression line was taken as the radial stiffness of the roll.

The measurement was repeated four times with further samples (toilet paper rolls from the same production batch), and the mean value of the five values obtained is taken as the radial stiffness K_(rad) of the roll.

5.8. Resiliency

The measurement is made by a vertical dynamometer (Zwickiline Z1.0) equipped with a 2.5 KN cell. The time was taken by a standard stopwatch timer.

A roll was placed horizontally between the pressure plates (dimensions: 190×190×15 mm), and the upper plate is lowered until the detected force is (0±0.1)N. The distance between the two pressure plates (corresponding to the external diameter of the roll) was measured and taken as the initial height H(i) of the roll.

Pressure was applied and, at the same time, the timer was started (t=0 sec.). The roll was compressed between the pressure plates at a constant speed of 400 mm/min until a maximum force of 10N was reached. The distance (i.e., the height of the roll) between the two pressure plates after the maximum force of 10N has been reached was measured and taken as H(10N). The pressure was released such that the pressure plates can return to their initial position at a speed of 800 mm/min.

At a time of 30 seconds, the height of the roll H(30 s) was measured.

The resiliency of the roll R was calculated using the following equation:

$\left( {R\mspace{14mu} \%} \right) = \frac{{H\left( {30s} \right)} - {H\left( {10N} \right)}}{{H(i)} - {H\left( {10N} \right)}}$

The resiliency measurement was repeated four times with further roll samples, and the mean value of the five values obtained was taken as resiliency of the roll measured.

5.9. Intersheet Adhesion (Delamination Force)

The measurement is made by a vertical dynamometer (39) (ZwickiLine Z1.0) equipped with a shaft assembly (40)-(43), a jaw (45) and a 50N cell (not shown) as depicted in FIGS. 9a, 9b and 9 c.

For the measurement, the first inner turns of a coreless roll to be measured (44) were inserted on the upper shaft (41) of the shaft assembly, the outermost paper sheet was unwound and placed on the shaft assembly as shown in FIG. 9a , and the outermost paper sheet was inserted into the jaw (45). The turns were unwound at a constant speed of 300 mm/min. The delamination force needed for separating the paper sheets forming the turns was measured and plotted as a function of the displacement of the cell. The maximal force and the average force required to delaminate the sample were recorded within the displacement interval. The delamination force measurement was then repeated four times with further samples.

The mean value of the 5 values of the maximal force obtained is taken as the delamination force of the coated continuous web.

5.10. Charge Demand

The measurement can be conducted as follows by polyelectrolyte titration using a particle charge detector PCD 03 pH available from BTG Mütek GmbH, Germany.

A sample solution of the polymer in water is prepared (e.g., 0.1 wt.-%) and transferred to the particle charge detector. The streaming current of the sample solution is monitored and a titrant (polyDADMAC 0.001N) is added until the point of zero charge is reached (i.e., measured streaming current=0 mV). The specific charge quantity q (ionic demand in [eq/g]) can be calculated using the following equation:

$q = \frac{V \times c}{m}$

wherein V [L] represents the consumed volume of titrant (polyDADMAC), c [eq./L] represents the concentration of the titrant, and m [g] represents the amount of polymer in the sample solution.

5.11. Disintegrability

The disintegrability can be determined according to NF Q34-20:1998, Sanitary and Domestic Articles—Bathroom Tissue—Determination of Disintegration.

5.12 Collapsing

The test can be conducted by a vertical dynamometer (ZwickiLine Z1.0) equipped with a 1 kN cell.

A roll is placed horizontally (on the round edge) between the pressure plates. The roll is compressed between the pressure plates at a constant speed of 400 mm/min until an oval cross section is reached, i.e., the axial passageway is not visible. The roll is maintained in the compressed form for a time of about 10 seconds, and the pressure is released such that the pressure plates can return to their initial position at a speed of 800 mm/min. The compression cycle is repeated 4 times.

The test is repeated four times with further samples (toilet paper rolls from the same production batch). Collapsing of the roll sample is evaluated by visual inspection of the first inner turns forming the reopened axial hollow passageway.

In the following, collapsing=“yes” means that peeling of the first inner turns at the reopened axial hollow passageway can be observed in at least one out of 5 tested roll samples. Collapsing=“no” indicates that no peeling of the first inner turns can be observed in all 5 tested roll samples, i.e., the reopened axial hollow passageway is well defined and the roll can be easily mounted on the spindle of a roll holder.

5.13. Starting Materials, Chemicals and Converting Machine Absorbent Material

A three-ply base tissue paper (Conventional) having a basis weight of 55.6 g/m² and a caliper of 0.62 mm (manufactured by SCA) was used as the continuous web of absorbent material in Reference Examples 1 to 3, Examples 1 to 7 and Comparative Examples 1 to 4.

The three-ply base tissue paper (continuous web) was prepared with a conventional converting machine by combining a one-ply base tissue paper to the final ply count (3) as follows:

A first unwinding unit provided a first ply of base tissue from a first parent roll having a width of 0.6 m. A second unwinding unit provided a second ply of base tissue from a second parent roll having a width of 0.6 m. A third unwinding unit provided a third ply of base tissue from a third parent roll having a width of 0.6 m. The plies of base tissue were fed to an embossing unit. The base tissues were superposed and combined (associated) using an adhesive in the embossing unit in order to form a continuous web of absorbent material. The engraved cylinder performed a double-level engraving into the superposed absorbent log base webs. The adhesive used for ply bonding was Swift® tak 1004 in an amount of 0.5 g/m².

The resulting three-ply continuous web of absorbent material was fed to a rewinding unit.

Chemicals

The chemicals used in the following examples are listed below:

For the coating composition:

-   -   Hydroxypropylmethyl cellulose from Sigma-Aldrich with         hydroxypropoxyl content of about 9% and viscosity of about 15 cP         (2% solution in water at 25° C.).

Adhesives:

-   -   Swift® tak 1004 from H. B. Fuller (used for ply bonding);     -   Tissue Tak 604 from Henkel (“fugitive glue” used for winding).

Converting Machine

A conventional tissue paper converting machine was adapted to make a toilet paper having three plies. The machine involved two unwinding units, an embossing unit, a rewinding unit, and a log cutting unit.

The embossing unit comprised an engraved cylinder, a mating rubber cylinder and a glue dispenser. The engraved cylinder was engraved with a microstructure pattern combining various embossing tips. The glue dispenser comprised a vat, an applicator and a dipping cylinder.

The rewinding unit comprised a perforating module, a cutting module, a winding module and an extraction module. The perforating module comprised a perforator roll and a stationary anvil roll. The cutting module comprised a cutting roll and a stationary anvil roll.

The rewinding unit was furthermore equipped with a spraying system consisting of four spray guns type WA520 (available from Walther Pilot) having a nozzle diameter of 1.5 mm and working under a pressure of 1.5, 2.0 or 2.5 bars, a vat and pipes feeding the coating composition from the vat to the spray guns.

The spray guns were placed between the cutting module and the winding module such that the coating composition was sprayed on the lower side of the continuous web of absorbent material upstream to a cutting line at the beginning of the log, thus defining the first web end (i.e., the turns of the log/roll close to the axial hollow passageway).

The log cutting unit comprised multiple log saws.

Various rollers are appropriately positioned in order to control the path of the absorbent log base webs along the converting machine, within and between the various units. The absorbent log base webs travel into the converting machine according to the machine direction (MD) from the unwinding units, towards the embossing unit, towards the rewinding unit and towards the log cutting unit.

A control module was coupled to the rewinding module, the perforating module, the cutting module and the spray guns by means of an interface. The control module controlled the operations of the perforating module, the cutting module and the appropriate spraying of the coating composition onto the second end as well as the winding force applied to the continuous web of absorbent material in the rewinding unit.

The machine speed was kept throughout the trials at 100 m/m in.

Reference Example 1 (Reference Toilet Paper with Density 93 mg/cm³)

To obtain the desired coreless roll of toilet paper, a three-ply continuous web of absorbent material (basis weight: 55.6 g/m², caliper: 0.62 mm) was produced as described above, conveyed from the embossing unit and fed to the rewinding unit.

In the rewinding unit, the continuous web first reached the perforating module, which pinched the web to provide perforation lines transversally orientated relative to the machine direction (MD) and regularly spaced relative to the cross direction (CD). The size of the perforated segment was 4 mm and the size of the unperforated segment was 1 mm. The distance between two perforation lines was 125 mm.

After pinching, the web of absorbent material reached the winding module, in which the web was picked up onto a temporary core (external diameter: 38 mm) using Tissue Tak 604 as “fugitive adhesive”. The continuous web (approximate total length of the continuous web: 17500 mm; corresponding to 140 perforated sheets) was then wound onto the core to form a log having a diameter of 120 mm.

The produced log was separated from the web of absorbent material by the cutting module, which severed the web transversally relative to the MD. The produced log was stored at 20-22° C., relative humidity of 50% for a period of 12 hours.

After storage, the temporary core was extracted from the log by the extraction module. The produced log was cut parallel to the MD by multiple log saws into multiple individual rolls having a width of 99 mm.

The density of the roll was 93 mg/cm³.

Reference Example 2 (Reference Toilet Paper with Density 119 mg/cm³)

A coreless roll was produced in the same manner as described in Reference Example 1 above except that a three-ply continuous web of absorbent material having an approximate total length of 22500 mm (corresponding to 180 perforated sheets) was wound onto the core to form a log having a diameter of 120 mm.

After storage, the temporary core was extracted from the log by the extraction module, and the log was cut parallel to the MD by multiple log saws into multiple individual rolls having a width of 99 mm.

The density of the roll was 119 mg/cm³.

Reference Example 3 (Reference Toilet Paper with Density 149 mg/cm³)

A coreless roll was produced in the same manner as described in Reference Example 1 above except that a three-ply continuous web of absorbent material having an approximate total length of 28125 mm (corresponding to 225 perforated sheets) was wound onto the core to form a log having a diameter of 120 mm.

After storage, the temporary core was extracted from the log by the extraction module, and the log was cut parallel to the MD by multiple log saws into multiple individual rolls having a width of 99 mm.

The density of the roll was 149 mg/cm³.

Example 1 (Toilet Paper with HPMC and Density 93 mg/cm³)

A coating composition was prepared by dissolving hydroxypropylmethyl cellulose (HPMC) in water at a concentration of 3.7% by weight. The obtained coating composition was fed to the spray guns and applied at room temperature (22° C.).

To obtain the desired coreless roll of toilet paper, a coreless roll was produced in the same manner as described in the Reference Example 1 above except that, after pinching/severing and before winding the web, the coating composition was applied (sprayed) by means of the spray guns (pressure: 2.5 bars) onto a length of about 3500 mm (i.e., about 20% of the entire web length) upstream from the cutting line.

The amount of HPMC applied onto the continuous web was 0.148 g/roll (solid content of HPMC applied to one individual roll, i.e., after cutting the log).

The density of the roll was 93 mg/cm³.

Examples 2, 3, 4 and 5 (Toilet Papers with HPMC and Density 93 mg/cm³)

Further coreless rolls of toilet paper were produced in the same manner as described in Example 1 above except that the application length, application pressure and dry polymer amount applied onto the continuous web in Examples 2, 3, 4 and 5 were as indicated in Table 1 below.

The density of the rolls produced in Examples 2, 3, 4 and 5 was 93 mg/cm³.

Examples 6 and 7 (Toilet Papers with HPMC and Density 119 mg/cm³)

Coreless rolls of toilet paper were produced in the same manner as described in Reference Example 2 above except that after pinching/severing and before winding the web, a coating composition as used in Example 1 above (3.7 wt.-% HPMC in water) was applied (sprayed) by means of the spray guns onto the continuous web.

The application length, application pressure and dry polymer amount applied onto the continuous web in Examples 6 and 7 were as indicated in Table 1 below. The density of the rolls produced was 119 mg/cm³.

Comparative Examples 1 and 2 (Toilet Papers with HPMC and Densities 93 mg/cm³ and 119 mg/cm³)

Coreless rolls of toilet paper were produced in the same manner as described in Reference Examples 1 or 2 above except that after pinching/severing and before winding the web, a coating composition as used in Example 1 above (3.7 wt.-% HPMC in water) was applied (sprayed) by means of the spray guns onto the continuous webs.

The application length (Comp. Ex. 1: 1750 mm/10% web length; Comp. Ex. 2: 3500 mm/16% web length), application pressure and dry polymer amount applied onto the continuous webs in Comp. Ex. 1 and 2 were as indicated in Table 1 below.

The density of the rolls produced was 93 mg/cm³ and 119 mg/cm³, respectively.

Comparative Examples 3 and 4 (Toilet Papers with HPMC and Density 149 mg/cm³)

Coreless rolls of toilet paper were produced in the same manner as described in Reference Example 3 above except that after pinching/severing and before winding the web, a coating composition as used in Example 1 above (3.7 wt.-% HPMC in water) was applied (sprayed) by means of the spray guns onto the continuous web.

The application length, application pressure and dry polymer amount applied onto the continuous web in Comparative Examples 1 and 2 were as indicated in Table 1 below. The density of the rolls produced was 149 mg/cm³.

The properties of the toilet paper rolls produced were evaluated according to the procedures described herein before. The results are shown in table 1 below.

TABLE 1 Roll density (mg/cm³) 93 (total length: 17500 mm) Ref. Comp. Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Application (mm) — 3500 7000 8750 13125 16800 1750 length (%) — 20 40 50 75 96 10 Application pressure — 2.5 2.0 2.0 2.5 2.5 2.0 (bars) Amount of coating 0 0.148 0.178 0.189 0.400 0.381 0.041 composition (g/roll) Stiffness Axial 190 240 267 365 357 300 232 (N/mm) K_(ax) Radial 0.41 0.54 0.62 — 0.78 0.79 — K_(rad) Resiliency (%) 66 82 86 91 92 95 72 Intersheet adhesion (N) 0.23 — 0.54 0.77 0.43 0.39 0.37 Perforation breakage No — No No No No No and/or sheets damaged Collapsing Yes No No No No No No Roll density (mg/cm³) 119 149 (total length: 22500 mm) (total length: 28125 mm) Ref. Comp. Ref. Comp. Comp. Example 2 Example 6 Example 7 Example 2 Example 3 Example 3 Example 4 Application (mm) — 9000 16875 3500 — 11250 14063 length (%) — 40 75 16 — 40 50 Application pressure — 2.0 2.0 1.5 — 2.0 2.0 (bars) Amount of coating 0 0.167 0.366 0.070 0 0.122 0.215 composition (g/roll) Stiffness Axial 249 333 321 — 478 504 444 (N/mm) K_(ax) Radial 0.72 1.16 1.33 0.89 1.30 1.46 1.58 K_(rad) Resiliency (%) 70 93 91 72 79 77 78 Intersheet adhesion (N) 0.24 0.60 0.76 0.50 0.28 0.80 0.47 Perforation breakage No No No No No No No and/or sheets damaged Collapsing Yes No No No Yes No No

These test data show that, according to the present invention, the application of a specific coating composition to the second end of a continuous web and at least 20% of the entire length of the continuous web, if combined with a suitable density of the coreless roll, leads to remarkable resiliency values and several other advantages. The inner turns of the resulting coreless rolls show a very good resistance to collapsing. At the same time, the intersheet adhesion (delamination force) of the roll is maintained in an acceptable range. Furthermore, it is easily possible to compress the coreless rolls, which is difficult if the density of the roll is much higher than 140 mg/cm³. This compressibility in combination with the resiliency of the roll leads to a superior product that can be stored in a compressed state but assumes again, to a very great extent, the original shape and appearance if the compressive forces are released.

Further, the respective coated continuous web materials produced in the examples of the invention were found to be disintegrable in accordance with the aforementioned test.

Furthermore, the rolls according to the present invention can be unwound up to the last sheet without tearing apart and/or damaging the sheets (i.e., no occurrence of perforation breakage and/or sheets damage in the delamination force measurement).

While the present invention has been illustrated by description of various embodiments and while those embodiments have been described in considerable detail, it is not the intention of Applicant to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications will readily appear to those skilled in the art. The present invention in its broader aspects is therefore not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of Applicant's invention. 

What is claimed is:
 1. A coreless roll of an absorbent sheet product made of a spirally wound continuous web of absorbent material having a first end and a second end, the web of absorbent material being wound such as to define an axial hollow passageway centrally positioned relative to the coreless roll and extending from one edge to another edge of the coreless roll and such that the first end is located on the outer side of the roll and the second end is located at the axial hollow passageway; wherein the spirally wound continuous web of absorbent material has a density of from 50 to 140 mg/cm³, preferably of 60 to 130 mg/cm³, more preferably of 70 to 120 mg/cm³; wherein at least a last turn located at the second end of the continuous web of absorbent material comprises a coating composition comprising a polymer including oxygen and/or nitrogen atoms, a turn being one circumvolution of the spirally wound continuous web about the axial hollow passageway; and wherein at least 20%, preferably at least 25%, more preferably at least 30%, more preferably at least 35%, more preferably at least 40%, more preferably at least 50%, more preferably at least 70% of the entire length of the continuous web of absorbent material in the machine direction comprises a coating composition comprising a nonionic polymer including oxygen and/or nitrogen atoms.
 2. The coreless roll of claim 1, wherein the coating composition is applied to only one side of the continuous web of absorbent material.
 3. The coreless roll of claim 1, wherein the polymer including oxygen and/or nitrogen atoms comprised in the coating composition applied to at least the last turn located at the second end is a nonionic polymer.
 4. The coreless roll of claim 1, wherein a maximum intersheet adhesion between the coated portions of the continuous web of absorbent material and the portions of the continuous web being in contact therewith is of from 0.3 to 1.7N.
 5. The coreless roll of claim 1, wherein the coating composition that is applied to the continuous web of absorbent material has an ionic demand of −1000 to +100 μeq/g, preferably of −500 to +50 μeq/g, more preferably of −50 to 0 μeq/g.
 6. The coreless roll of claim 1, wherein the nonionic polymer comprises at least one repeating unit comprising one or more oxygen and/or one or more nitrogen atoms.
 7. The coreless roll of claim 6, wherein the nonionic polymer comprises at least one repeating unit comprising one or more ether oxygen atoms and/or one or more hydroxyl groups.
 8. The coreless roll of claim 6, wherein on average at least 50%, preferably at least 80%, of all repeating units constituting the nonionic polymer comprise one or more oxygen and/or one or more nitrogen atoms.
 9. The coreless roll of claim 1, wherein the nonionic polymer is a nonionic cellulose ether.
 10. The coreless roll of claim 9, wherein the nonionic cellulose ether has a number-average molecular weight of 1,000 to 1,000,000, preferably of 2,000 to 500,000, more preferably of 3,000 to 200,000, more preferably 5,000 to 100,000.
 11. The coreless roll of claim 9, wherein the nonionic cellulose ether is an alkyl cellulose ether such as methylcellulose or ethylcellulose, a hydroxyalkyl cellulose ether such as hydroxyethyl cellulose or hydroxypropyl cellulose, or a combination thereof.
 12. The coreless roll of claim 1, wherein the nonionic polymer is a polyether polyol, preferably a polyether polyol selected from polyethylene glycol, polypropylene glycol, and mixtures thereof, more preferably polyethylene glycol, and wherein preferably at least 40%, more preferably at least 50%, more preferably at least 70% of the entire length of the continuous web of absorbent material in the machine direction comprises a coating composition comprising the polyether polyol.
 13. The coreless roll of claim 12, wherein the nonionic polymer has a number-average molecular weight of 800 to 250,000, preferably of 1,000 to 50,000, more preferably of 1,500 to 15,000, more preferably of 1,500 to 10,000, more preferably of 2,000 to 7,500, e.g. 2,500 to 4,000.
 14. The coreless roll of claim 1, wherein the coating composition comprises: (a) at least 50 wt.-%, preferably at least 65 wt.-%, more preferably at least 80 wt.-% of the nonionic polymer; (b) not more than 50 wt.-%, preferably not more than 35 wt.-%, more preferably not more than 20 wt.-% of further additives such as plasticizers, reinforcing agents, fragrance, and dyes; each based on the total solids content of the coating composition.
 15. The coreless roll of claim 1, wherein the coating composition is applied in molten form or, after the addition of water, as an aqueous solution, wherein the aqueous solution preferably contains the nonionic polymer in an amount of at least 0.1 wt.-%, more preferably at least 0.5 wt.-% based on the total weight of the coating composition.
 16. The coreless roll of claim 1, wherein at least the last two, preferably at least the last three turns, preferably at least the last five turns, more preferably at least the last ten turns located at the second end of the continuous web of absorbent material comprise the coating composition.
 17. The coreless roll of claim 1, wherein the coating composition is applied such that, with respect to the length portion or length portions of the continuous web that comprise(s) the coating composition, the area covered by the coating composition is at least 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90% of the total area of said length portion(s).
 18. The coreless roll of claim 1, wherein if the coating composition has been applied continuously in the machine direction, the resulting coated portion starts at the second end and includes at least the last turn of the second end.
 19. The coreless roll of claim 1, wherein if the coating composition has been applied intermittently in machine direction, thereby providing two or more coated portions, (i) one coated portion includes at least the last turn of the second end and (ii) the amount of nonionic polymer applied to the half of the continuous web including the second end is preferably equal to or greater than the amount of nonionic polymer applied to the half of the continuous web including the first end.
 20. The coreless roll of claim 1, wherein the total amount of nonionic polymer is from 0.001 to 40 g/roll, preferably 0.005 to 10 g/roll, more preferably 0.005 to 5 g/roll, in particular 0.01 to 2 g/roll.
 21. The coreless roll of claim 1, wherein the web of absorbent material is composed of at least 1 tissue paper ply.
 22. A coreless roll of an absorbent sheet product made of a spirally wound continuous web of absorbent material having a first end and a second end, the web of absorbent material being wound such as to define an axial hollow passageway centrally positioned relative to the coreless roll and extending from one edge to another edge of the coreless roll and such that the first end is located on the outer side of the roll and the second end is located at the axial hollow passageway; wherein the coreless roll has a resiliency at 30 seconds of at least 75%, preferably at least 80%, more preferably at least 85%, even more preferably at least 90%.
 23. The coreless roll of claim 22, wherein the roll has a diameter of 50 to 500 mm, preferably of 80 to 200 mm, more preferably of 100 to 155 mm.
 24. (canceled)
 25. The coreless roll of claim 1 being in a compressed form.
 26. The coreless roll of claim 1, which is an absorbent product selected from the group consisting of napkins, towels household towels, kitchen towels or hand towels, toilet papers, wipes, handkerchiefs, and facial tissues.
 27. A manufacturing method for manufacturing a coreless roll of an absorbent sheet product comprising: conveying a continuous web of absorbent material having a first end and a second end, which is composed of at least 1 tissue paper ply; optionally severing the continuous web of absorbent material substantially transversally to the machine direction to produce single but coherent sheets; applying a coating composition as defined in claim 1 to the continuous web; spirally winding the continuous web of absorbent material so as to produce a log of web of absorbent material, the web of absorbent material being wound such as to define an axial hollow passageway centrally positioned relative to the log and extending from one edge to another edge of the log and such that the first end is located on the outer side of the log and the second end is located at the axial hollow passageway; and cutting the log into multiple coreless rolls.
 28. The manufacturing method of claim 27, further comprising subjecting the coreless roll to compression in a direction perpendicular to the axial hollow passageway to produce a coreless roll in a compressed form.
 29. (canceled)
 30. (canceled)
 31. The coreless roll of claim 2, wherein the coating composition is applied to the side of the continuous web of absorbent material oriented towards the axial hollow passageway.
 32. The coreless roll of claim 21, wherein the at least 1 tissue paper ply comprises 2 to 6 superimposed tissue paper plies.
 33. The coreless roll of claim 8, wherein the at least 50%, preferably 80%, of all repeating units comprise one or more ether oxygen atoms and/or one or more hydroxyl groups.
 34. The manufacturing method of claim 27, wherein the at least 1 tissue paper ply comprises 2 to 6 superimposed tissue paper plies. 